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Early Human Development (2008) 84, 515523
a v a i l a b l e a t w w w. s c i e n c e d i r e c t . c o m
w w w. e l s e v i e r. c o m / l o c a t e / e a r l h u m d e v
BEST PRACTICE GUIDELINE
The changing face of haemolytic diseaseof the newborn
Irene A.G. Roberts
Department of Haematology, 4th Floor Commonwealth Building, Hammersmith Hospital, Du Cane Road, London W12 0NN,United Kingdom
KEYWORDS
Neonate;Hyperbilirubinaemia;Immune;Haemolytic;Transfusion;Immunoglobulin;Metalloporphyrin
Abstract
The diagnosis, acute management and follow-up of neonates with haemolytic disease of thenewborn (HDN) still represents a significant area of activity for maternity/neonatal services. ABOincompatability is now the single largest cause of HDN in the western world. However, withincreasing knowledge at the molecular level, and closer liaison between neonatal paediatriciansand haematologists, the diagnosis of non-immune causes of HDN is increasing. As these conditionshave an inherited basis and therefore have implications for other family members (or futurechildren), it remains a high priority for all neonatal paediatricians to achieve an accuratediagnosis in all cases of HDN. As the efficacy of phototherapy increases the role of exchangetransfusion in acute management is rapidly decreasing. This makes gauging the appropriate time
to intervene with exchange transfusion a difficult clinical decision, and guidelines appropriate tothe spectrum of contemporary disease are required. In the future intravenous immunoglobulinand/or intramuscular metalloporphyrins may further reduce the need for exchange transfusionand continue to change the spectrum of HDN faced by neonatal paediatricians. 2008 Published by Elsevier Ireland Ltd.
Contents
1.
2.3.4.5.6.7.8.
Clinical presentation of HDN . . . . . . . . . . . . . . . . . . . . . .
Severe unconjugated hyperbilirubinaemia. . . . . . . . . . . . . . .ABO incompatibility . . . . . . . . . . . . . . . . . . . . . . . . . . .Positive direct anti-globulin test . . . . . . . . . . . . . . . . . . . .Haemolysis in neonates with a known positive maternal antibody testScreening for maternal red cell allo-antibodies . . . . . . . . . . . . .Clinical significance of maternal red cell allo-antibodies . . . . . . .Anti-Kell antibodies . . . . . . . . . . . . . . . . . . . . . . . . . . .
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516516517517517518518
Tel.: +44 208 383 2163; fax: +44 208 742 9335.E-mail address: [email protected].
0378-3782/$ - see front matter 2008 Published by Elsevier Ireland Ltd.doi:10.1016/j.earlhumdev.2008.06.005
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Management of HDN due to red cell allo-antibodies . . . . . . . . .Intrauterine transfusion . . . . . . . . . . . . . . . . . . . . . . . . .Haemolysis detected on the blood film . . . . . . . . . . . . . . . .Prolonged hyperbilirubinaemia . . . . . . . . . . . . . . . . . . . . .How to distinguish HDN from other causes of neonatal haemolysis13.1. Red blood cell membrane disorders [23,24] . . . . . . . . .13.2. Red blood cell enzyme defects [2531] . . . . . . . . . . .13.3. Neonatal haemolysis due to haemoglobinopathies . . . . .13.4. Alpha thalassaemia major . . . . . . . . . . . . . . . . . . .
14. Developments in therapy for neonatal hyperbilirubinaemia. . . . .14.1. Improved phototherapy . . . . . . . . . . . . . . . . . . . .14.2. High dose intravenous immunoglobulin . . . . . . . . . . .14.3. Metalloporphyrins . . . . . . . . . . . . . . . . . . . . . . .
15. Practice points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16. Research directions . . . . . . . . . . . . . . . . . . . . . . . . . . .References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.10.11.12.13.
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I.A.G. Roberts
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518519519519519519519519520
520520520521521521522
In the space of most paediatricians working lifetime thespectrum of haemolytic disease of the newborn (HDN) haschanged beyond recognition. Thirty years ago HDN was almost
synonymous with rhesus (Rh) D allo-immunisation and was acommon neonatal problem. It was usually unmodified byantenatal therapy and caused overt fetal or neonatalhaemolysis leading to marked neonatal hyperbilirubinaemiaand attendant anaemia. Affected neonates were commonlysick and unstable at birth, required multiple exchangetransfusions and suffered considerable neonatal morbidityand mortality. However, the introduction of routine post-natalprophylactic anti-D immunoglobulin in the 1970s dramaticallyreduced this form of HDN making this one of the success storiesof modern perinatal care. This review aims to discuss HDN inthe context of contemporary neonatal services and review itsvarying presentations. The role of established therapies,particularly improved phototherapy, and potential new thera-pies, including intravenous immunoglobulin (IVIG), and intra-muscular metalloporphyrins will also be assessed.
neonate. If jaundice is clinically obvious within the first2448 h of life then the neonate may still be hospital-basedwith their mother. However, with increasing early maternal
discharge from maternity services many affected neonateswill be re-admitted from the community. In such cases theplasma bilirubin at presentation is often greater than300 mmol/L. The commonest cause of HDN presenting inthis way is that due to ABO incompatibility (see below).However, other clinically significant causes of neonatalhaemolysis may also present in this way (Table 1). Thereforeall neonates with early-onset, severe and/or prolongedhyperbilirubinaemia should be thoroughly investigated toexclude the possibility of neonatal haemolysis. This isespecially pertinent if common causes of HDN (e.g. ABOincompatibility) are excluded, but the degree of hyperbilir-ubinaemia cannot be satisfactorily explained by the neona-te's general course since birth (e.g. state of hydration/weight loss, establishment of feeding, concurrent neonatalcomplications i.e. infection).
1. Clinical presentation of HDN
Although the clinical burden imposed on neonatal services byHDN has greatly reduced, it has not disappeared. Neonatalpaediatricians continue to recognise a number of differentpresentations of neonatal haemolysis, many of which aremore subtle than the traditional neonatal emergencypresentation of severe RhD disease. HDN should be con-sidered where there is one or more of the following:
rapidly developing or severeunconjugated hyperbilirubinaemia;
a positive direct antiglobulin test (DAT); positive maternal antenatal antibody screening and/or aseverely anaemic or hydropic fetus;
haemolysis detected on blood film examination; prolonged hyperbilirubinaemia.
3. ABO incompatibility
ABO HDN occurs almost exclusively in the offspring of womenof blood group O (although reports exist of occasional casesin group A mothers with high titre anti-group B IgG [1]. Ingeneral 15 to 25% of all maternal/fetal pairs are ABOincompatible but ABO HDN is confined to the 1% of group Owomen that have high-titre IgG antibodies [2]. Haemolysisdue to anti-A is more common (1 in 150 births) than anti-B.Affected neonates will usually, but not always, be DATpositive. The proportion of cases of ABO HDN with a positiveDAT varies according to the laboratory reagents used; in arecent report 40% of babies requiring phototherapy due toABO incompatibility had a negative DAT [3]. In contrast to theclinical picture with anti-Rh antibodies, both anti-A and anti-B HDN usually result predominately in hyperbilirubinaemiawithout significant neonatal anaemia. This is mainly becauseof the relatively low numbers of group A or B sites onneonatal red cells, allowing the antibody-coated cells toremain in the circulation for a longer period than in Rh-Ddisease [4]. As a reflection of this the blood film in ABO HDNcharacteristically shows large numbers of spherocytes withlittle or no increase in nucleated red cells (nRBCs), whereas in
2. Severe unconjugated hyperbilirubinaemia
In contemporary neonatal practice HDN presenting in thisway is typically seen without predictive antenatal factors inthe early neonatal course of an otherwise well term
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The changing face of haemolytic disease of the newborn
Table 1 Causes of unexpected haemolytic diseasepresenting as early onset or rapidly progressivehyperbilirubinaemia
Causes andconditions
Comments
517
of black African origin. In such cases severe anaemia as wellas hyperbilirubinaemia [5] can occur and antenatal hydropsfetalis has been described [6]. The severity of hyperbilir-ubinaemia is increased in neonates who also have G6PDdeficiency and in those with Gilbert's syndrome [7].
ABO incompatability Usually maternal Usually DATgroup O, babypositive. Can be
group Asevere in cases ofmaternal group O,baby group B (wheremother is of Africanorigin)
UndiagnosedAnti-rhesusDAT positive.maternal allo-(D, E, c, C)Followingantibodiessensitizing event in
pregnancyAnti-KellDAT positive. May
present withmarked anaemiabut mildhyperbilirubinaemia
Red blood cellHereditaryDAT negative.membrane defects spherocytosisVariable clinical
Hereditarycourse.
eliptocytosisCharacteristic redHereditarycell morphology onpyropoikilocytosis blood film
Red blood cellG6PD deficiency DAT negative. Mayenzyme defectspresent with
markedhyperbilirubinaemiawithout anaemia orblood film signs ofhaemolysis
Pyruvate kinase DAT negative.deficiencyVariable clinical
course but severehyperbilirubinaemiapossible
Heamoglobinopathies Alpha-DAT negative. Maythalassemiararely present with
majorhydrops, severeanaemia andhyperbilirubinaemiain liveborn pretermneonates
4. Positive direct anti-globulin test
The direct anti-globulin test (DAT) is a screening test for non-agglutinating antibodies on red blood cells. If maternalserum contains an IgG class immunoglobulin directed againsta fetal red blood cell antigen transplacental passage of thisantibody will result in red blood cell antibody coating and apositive fetal and neonatal DAT. As a screening test on its ownthe DAT has a poor positive predictive value for identifyingneonates who require treatment of HDN by phototherapy.Dinesh [3] recently reported routine DAT screening of 1724cord blood samples collected over the first 6 months of 2001in Wellington, New Zealand. Of these 94 samples (5.5%)showed a positive DAT. However, only 23% of neonates foundto have a positive DAT on neonatal screening went on todevelop hyperbilirubinaemia requiring phototherapy and itwas only when the DATwas strongly positive (4+) that 100% of
such neonates required phototherapy. This study confirmedABO incompatibility as the main cause of HDN in modernneonatal practice as 76/94 cases of DAT positivity occurred inABO incompatible mother/neonate pairs. Only 6 cases of DATpositivity occurred in neonates where there was antenataldetection of maternal antibodies to red cell antigens withthe potential to cause HDN. It should also be appreciatedthat in a unit where RhD negative women receive routineantenatal anti-D immunoglobulin in the third trimester up to15% of the resulting neonates will have a positive DAT simplyfrom passive transfer of prophylactic anti-D administered tothe mother during pregnancy [8] These antibodies do notcause significant fetal or neonatal haemolysis and so nospecial postnatal investigation or monitoring of such neo-nates is required. If there is doubt about the cause of thepositive DAT in such neonates blood film examination will
point to the correct diagnosis as neither spherocytes nornRBCs will be present in unusual numbers.
5. Haemolysis in neonates with a known positivematernal antibody test
Although most acute presentations of neonatal haemolysisnow occur without warning, a significant number of cases of
HDN are predicted by the antenatal detection of knownmaternal red cell allo-antibodies.RhD HDN there are few spherocytes and large numbers ofcirculating nRBCs. Blood film examination is therefore usuallydiagnostic in DAT negative cases of suspected ABO HDN.
Management of ABO HDN is usually successful withphototherapy alone provided by modern equipment (seebelow). Recently the use of high dose intravenous immu-noglobulin (IVIG) has been assessed in ABO HDN and thistherapy may be beneficial in selected cases (see below).Even with these therapies close monitoring of the affectedneonate is essential as exchange transfusion is occasionallyrequired. This is particularly the case in ABO HDN due to anti-B antibodies where racial differences in disease severityexist - severe cases being prevalent in mothers and neonates
6. Screening for maternal red cell allo-antibodies
Recent large population screening studies demonstrate theprevalence of anti-RhD antibody has greatly reduced reflect-ing the reduction in RhD alloimmunisation achieved by theuse of prophylactic anti-D immunoglobulin. Geifman-Holtz-man et al. [9] reported antibody screening in 37 506 femaleserum samples, the majority of which were from women ofreproductive age. Of the total, 452 (1.2%) showed positiveantibody screens. In these positive women the frequencies of
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518
specific antibodies were: anti-D, 18.4%; anti-E, 14%; anti-c5.8%; anti-C, 4.7%; anti-Kell group, 22%; anti-MNS, 4.7%; anti-Fya (Duffy), 5.4%; and anti-Jka, (Kidd) 1.5%. This gives anoverall rate of anti-D positivity of 2.6 per 1000 samplesanalysed, compared with 43.3 per 1000 samples reported in astudy by Polsky et al. in 1967. In a further study assessingantibody screening in 21 730 pregnant women in Yugoslavia,630 samples gave positive screens: 254 being anti-D and 376other antibodies. However, only 522 samples (2.4% overall)
were felt to contain clinically significant antibodies.
I.A.G. Roberts
proliferation of these cells may be responsible for thethrombocytopenia and leukopenia sometimes seen in new-borns with HDN due to anti-Kell [12]. In anti-Kell disease thelack of a consistent correlation between the degree of fetalanaemia and the standard methods of monitoring pregnan-cies affected by HDN (maternal antibody titres and amnioticfluid OD 450) has previously made the assessment of suchpregnancies problematic. This has lead to recommendationsthat such pregnancies should be monitored closely with the
use of repeated estimation of fetal haemoglobin concentra-tion by cordocentesis. However, non-invasive methods toassess the risk of fetal anaemia are now being developed andvalidated to reduce the need for repeated invasive proce-dures in such pregnancies (see below).
7. Clinical significance of maternal red cellallo-antibodies
Despite this reduction in the prevalence of anti-D antibodies,anti-D continues to be the commonest antibody leading tofetal and neonatal morbidity and mortality. Howard et al.[10] report a study of antenatal antibody screening in 22 264women, including the fetal and neonatal outcomes in womenwith positive antibody screens to antigens known to causeHDN. Clinically important antibodies were detected in 244(1%) of women, of which 100 were anti-D, 73 were directedagainst other Rh antigens, and 71 were non-rhesus antibodies(anti-Kell being most common). In these antibody positivepregnancies there were 3 intrauterine deaths and 3 fetuseswere given intrauterine transfusions. Exchange or top-uptransfusions were required in 10 neonates and 27 otherneonates had phototherapy. However, the most significantclinical outcomes including: fetal loss prior to 24 weeksgestation, intrauterine death, and the requirement forintrauterine red cell transfusion and/or post-natal exchangetransfusion were all more frequent in the fetuses andneonates of mothers with anti-D antibodies. In this studythe other maternal antibodies most commonly associat-ed with adverse fetal and neonatal outcomes were: anti-c,anti-E, and anti-Kell (although numbers of affected fetuses/neonates are too small for meaningful comparisons ofseverity of outcome related to maternal antibody type).
9. Management of HDN due to redcell allo-antibodies
Although detailed descriptions are beyond the scope of thisreview, significant advances have been made in themonitoring of fetuses where maternal red cell allo-anti-
bodies put the fetus at risk of haemolysis. Antenatal bloodgroup genotyping by polymerase chain reaction (PCR) fromfetal cells obtained by amniocentesis [13] or, more recently,from maternal blood samples [1416] helps to differentiatesusceptible form non-susceptible fetuses. In addition, asses-sing the degree of fetal anaemia non-invasively by middlecerebral artery Doppler studies reduces the need forrepeated invasive procedures [17]. For a more detailedoverview of these advances the reader is referred to recentreviews [18,19]. The management of affected neonates requires close co-operation between obstetric, neonatal and haematologyteams. All neonates at risk should have cord blood taken formeasurement of haemoglobin, DAT and bilirubin (to confirmthe diagnosis and assess the need for postnatal therapy). Allpotentially affected neonates should remain in hospital until
hyperbilirubinaemia and/or anaemia have been properlyassessed and managed and appropriate follow-up arranged.Trial evidence is lacking to support the use of prophylacticphototherapy in affected neonates [20],but in busy post-natalwards this approach at least ensures that those who requireeffective phototherapy receive it in a timely manner and thismay avoid exchange transfusion in a small number of neonates.
Appropriate guidelines for exchange transfusion in neo-nates with HDN are more controversial. Established guide-lines suggest exchange transfusion in HDN is required for:
severe anaemia: haemoglobin b 10 g/dL at birth (with thepossible exception of anti-K which as outlined above cancause significant anaemia without marked hyperbilirubi-naemia) and/or
severe hyperbilirubinaemia (total serum bilirubin N350N 10 mmol/L per hour).
However, these values are derived from clinical experiencein preventing kerniterus in sick neonates with untreated RhDHDN (an increasingly uncommon presentation). As outlinedpreviously the typical presentation of HDN is now the wellterm neonate with ABO incompatibility who presents with atotal serum bilirubin already in excess of 300 mmol/L (often as
8. Anti-Kell antibodies
HDN due to anti-Kell antibodies appears to have distinctfeatures compared to other commonly occurring maternalantibodies. The degree of fetal and neonatal anaemia in Kellalloimmunised pregnancies can be severe and may be themain clinical feature of the disease without significanthyperbilirubinaemia. Neonatal nucleated red blood cellcounts (reflecting fetal erythropoietic activity) may also be
inappropriately low. In addition, the degree of fetal anaemiais not well reflected by maternal anti-Kell antibodies titres orby amniotic fluid OD 450. All of these features point to adegree of fetal erythropoietic suppression as part of theclinical picture in anti-Kell alloimmunised pregnancies. Thisfeature of the disease was confirmed by Vaughan et al. [11]who found that using an in-vitro culture system the growth ofKell positive neonatal erythroid progenitor cells was inhib-ited by the addition of anti-Kell antibodies, suggesting thiswas, at least in part, the mechanism responsible for theanaemia seen in anti-Kell HDN. It has subsequently beendemonstrated that Kell antigens are present on othermyeloid progenitor cells and that inhibition of the fetal
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The changing face of haemolytic disease of the newborn
a readmission from home), without significant anaemia.Intensive phototherapy (during the 46 h it normally takes toobtain appropriate blood product and organise exchangetransfusion) almost always results in a significant drop in thetotal serum bilirubin. Such neonates may also be candidatesfor therapy with IVIG (see below) as this will almost certainlybe available more quickly than blood for exchange transfusion.This causes a practical clinical dilemma as the blood product(s)used for exchange transfusion in the UK are in short supply and
potential wastage has to be avoided. Therefore, whilst theseguidelines for exchange transfusion remain pertinent foruntreated HDN associated with defined antenatally-detectedmaternal antibodies, the majority of cases must now beassessed individually depending upon the general condition ofthe neonate (state of hydration, gestational and post-natalage), family history, an accurate clinical/laboratory diagnosisand the initial response to modern intensive phototherapy (seebelow). Following this approach the majority of largematernity/neonatal services now perform only a handful ofexchange transfusions per year without apparent detriment tothe long-term health of neonates affected by HDN [21].
519
12. Prolonged hyperbilirubinaemia
All neonates with prolonged hyperbilirubinaemia should bethoroughly investigated to exclude the possibility of HDN(Table 1). Persistent jaundice is a common presentation of HDNand virtually all the conditions mentioned in this review maypresent with prolonged hyperbilirubinaemia. Achieving thecorrect diagnosis may well have implications not only for the
jaundiced neonate but also for other family members.
13. How to distinguish HDN from other causesof neonatal haemolysis
13.1. Red blood cell membrane disorders [23,24]
The main clues that a neonate with early-onset or rapidlyprogressive hyperbilirubinaemia has a red cell membranedisorder are a family history, negative DAT and an abnormalblood film. The most common red cell membrane disorder topresent with neonatal hyperbilirubinaemia is hereditaryspherocytosis. Most affected neonates are not anaemic but asmall number require transfusion. The diagnosis is usuallymade by the combination of the characteristic red cellspherocytosis on the blood film and family history butmore specialised tests such as red cell dye-binding studiesor membrane electrophoresis may be helpful in difficult cases.The other red cell membrane disorders that may present withneonatal hyperbilirubinaemia are hereditary elliptocytosis andhereditary pyropoikilocytosis (HPP), both of which are identi-fied by examination of the blood film.
10. Intrauterine transfusion
Neonates who have received repeated intrauterine transfu-sions (IUT) for treatment of haemolysis have an alteredneonatal course. The effect of the first intrauterine transfu-sion on fetal haemoglobin is short-lived due the presence ofresidual antibody-coated fetal RBC. However, with subse-quent IUT fetal haemopoiesis is suppressed so that newbornswho have been transfused until near term, neonatal jaundiceis usually mild, they may require no or minimal phototherapy,and neonatal anaemia is absent [22]. By contrast lateanaemia in such neonates is common as the haemopoieticsuppression induced by IUT may last for many weeks followingdelivery. Management of such neonates is expectant, initially
ensuring adequate nutritional support (including appropriateiron and folic acid supplementation). Following dischargemonitoring of haemoglobin concentration, blood film mor-phology, reticulocyte count and bilirubin is necessary togauge when haemolysis has stopped and endogenous red cellproduction has re-commenced. The appropriate interval forthis must be tailored to the individual neonate taking intoconsideration the extent of the underlying haemolysis and,most importantly, the general condition and growth anddevelopment of the affected neonate (simply bleeding suchneonates weekly often only raises maternal anxiety withoutnecessarily adding useful clinical information). Red celltransfusions are only required in those with symptomaticanaemia (notoriously difficult to evaluate clinically) withmost neonates requiring no RBC top-ups, although in someclinically well neonates the haemoglobin level may fall as low
as 5 g/dL before rising spontaneously (personal experience).
13.2. Red blood cell enzyme defects [2531]
Inherited red cell enzyme deficiencies, especially glucose-6-phosphate dehydrogenase (G6PD) deficiency, are a relativelycommon cause of neonatal hyperbilirubinaemia. G6PD defi-ciency presents with early-onset unconjugated hyperbilirubi-naemia, which is often severe; significant anaemia isuncommon (refs). It is seen in all ethnic groups with a highprevalence in individuals from central Africa (20%) and theMediterranean (10%). It is X-linked and so mainly affects malesalthough female heterozygotes occasionally develop neonataljaundice. The main clues to this diagnosis are the negative DAT,ethnic origin and gender, early onset and usually normal bloodfilm; the diagnosis is made by assaying G6PD in peripheralblood cells. Pyruvate kinase (PK) deficiency is the second mostcommon red cell enzymopathy in neonates. It is autosomalrecessive and clinically heterogeneous with presentationvarying from hydrops fetalis through severe early onset
neonatal hyperbilirubinaemia requiring exchange transfusionto a mild unconjugated hyperbilirubinaemia. The diagnosis ismade by measuring pre-transfusion red cell PK activity; theblood film is sometimes distinctive but more often shows non-specific changes of non-spherocytic haemolysis.
11. Haemolysis detected on the blood film
In modern neonatal practice haemolysis may be detectedduring routine blood film examination (e.g. during review forevidence of neonatal sepsis). This emphasises the impor-tance of requesting blood film examination on all neonateswith non-physiological jaundice (Table 1).
13.3. Neonatal haemolysis due tohaemoglobinopathies
The haemoglobinopathies, with the exception of alpha-thalas-saemia major, do not usually present in the neonatal period.
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520 I.A.G. Roberts
are employed correctly (i.e. ensuring correct distancebetween device and patient, proper maintenance and servi-cing of phototherapy units). Phototherapy units are nowsmaller, easier to use around the cot, more efficient -particularly high-intensity gallium nitride light-emittingdiodes (LEDs) [38,39], and more powerful- the total irradiancethat can be applied to an individual neonate has vastlyincreased. In short phototherapy is now a viable alternative tothe planned use of exchange transfusion in the therapy of even
moderate to severe HDN [40], and as devices continue todevelop and improve phototherapy is likely to play an evengreater role in the therapy of HDN. For a fuller description ofdevelopments in neonatal phototherapy since its first use thereader is referred to recent reviews [36,41].
13.4. Alpha thalassaemia major
Alpha-thalassaemia major occurs when all 4 alpha-globingenes on chromosome 16 are deleted [32]. It predominantlyaffects families of south east Asian origin and presents withmid-trimester fetal anaemia or hydrops fetalis which is fatalwithin hours of delivery (occasional babies have lived a fewdays). It can occasionally cause diagnostic confusion if a fetus
developing the marked anaemia and hydrops characteristic ofthe condition is delivered preterm and rapidly then developshyperbilirubinaemia. Therefore, the diagnosis of alpha-tha-lassaemia major should be suspected in any case of severefetal anaemia presenting in the second trimester and any caseof hydrops fetalis with severe anaemia in which the parentscome from south east Asia ( it is also seen occasionally infamilies who originate from India, the Middle East or theMediterranean). Checking the blood counts of the parents willimmediately identify whether they are at risk of having a childwith alpha-thalassaemia major- both parents will be carriers ofa chromosome 16 in which both of the 2 alpha-globin genes aredeleted and so they will have hypochromic, microcytic red cellindices (MCV usually b 74 fl and MCH usually b24 pg). Thediagnosis of alpha-thalassaemia major is confirmed by Hbelectrophoresis or HPLC (which shows only Hb Barts and HbPortland; HbF and HbA are absent). The blood film showshypochromic, microcytic red cells with vast numbers ofcirculating NRBCs. Neonatal management of alpha-thalassae-mia major has no impact on survival unless the baby hasreceived a planned programme of intrauterine transfusions.For fetuses/neonates treated in this way post-natal manage-ment is the same as for beta-thalassaemia, i.e. life-long redcell transfusions or bone marrow transplantation after the ageof 2 years [33,34].
14.2. High dose intravenous immunoglobulin
In the last 1015 years a number of studies of high doseintravenous immunoglobulin (IVIG) as adjuvant treatment forHDN have been published [4247], and two systematicreviews have been carried out [48,49]. In 2004 Miqdadet al. [42] reported the use of IVIG in a study of 112 well term
neonates with hyperbilirubinaemia resulting from DAT-positive ABO HDN. In addition to phototherapy the interven-tion group (n = 56) received 500 mg/kg IVIG over 4 h if theserum bilirubin was rising by 8.5 mmol/L per hour or greater.Exchange transfusion was carried out in all neonates if theserum bilirubin exceeded 340 mmol/L, or was r ising bygreater than 8.5 mmol/L per hour in the phototherapy onlygroup. In the phototherapy only group 16 neonates weretreated with exchange transfusion whereas only 4 neonatesin the IVIG group required exchange transfusion. Theduration of phototherapy was also reduced in the IVIGgroup. No side-effects of IVIG were seen. Similar results wereseen in a study reported by Alpay et al. in 1999 [44]. Theystudied 116 neonates with hyperbilirubinaemia resultingfrom DAT-positive ABO or Rh HDN of whom 58 received IVIG1 g/kg over 4 h when the serum bilirubin exceeded
204 mmol/L. Exchange transfusion was performed if theserum bilirubin exceeded 290 mmol/L or was rising by morethan 17 mmol/L per hour. In the phototherapy only group 22neonates were treated with exchange transfusion whereasonly 8 neonates in the IVIG group required exchangetransfusion. Again the duration of phototherapy and hospitalstay were significantly reduced in the IVIG group. No adverseeffects of IVIG were reported. Similar results have beenfound in previous smaller studies assessing the use of IVIG inthe treatment of HDN. Despite the positive benefits of IVIGsuggested by these studies there are methodologicaldifficulties and questions about the safety of IVIG thatpotentially limit the size of the role IVIG may have in thetreatment of HDN. The preponderance of ABO HDN in thelarger studies suggests that the neonates assessed arerelatively well and the vast majority would be expected to
respond to intensive phototherapy alone unless low thresh-olds for exchange transfusion (bilirubin 290340 mmol/L)are employed. There is also variation in the timing ofadministration and dose of IVIG between studies. Lateanaemia may be more prevalent in those treated with IVIG,presumably because fewer neonates have exchange transfu-sion and therefore removal of maternal antibody. No majorside effects have been reported in the neonates treated with
14. Developments in therapy for neonatalhyperbilirubinaemia
14.1. Improved phototherapy
The changing clinical practice surrounding HDN is, in no smallway, the result of improvements in both the understandingand delivery of phototherapy. Phototherapy was firstintroduced for the treatment of neonatal hyperbilirubinae-mia in the late 1950s [35], when white light was the mainstayof treatment. Since then considerable advances have beenmade and it is now appreciated more fully that the efficacyof phototherapy in reducing neonatal hyperbilirubinaemia isdependant on a number of factors [36]:
the spectral qualities of the delivered light (optimal wavelengthrange 400520 nm, with peak emissions of 460 nm)
irradiance (intensity of light) [37] body surface area receiving phototherapy skin pigmentation total serum bilirubin concentration at commencement ofphototherapy
duration of exposure.
Modern phototherapy devices are designed to maximise theefficacy of phototherapy to the neonate and clinicians aremore appreciative of the importance of ensuring such devices
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IVIG but since IVIG is a pooled blood product the potential fortransmission of blood borne infections remains [50,51]. Given these facts how should neonatal paediatriciansapproach the use of IVIG in patients with HDN. The currenttrial evidence clearly points to positive benefits, particularlythe reduction in the need for exchange transfusion. Paedia-tricians are less experienced with this technique due to thereduction of RhD disease and so morbidity associated with thisprocedure may increase in the future. Therefore the use of a
more straightforward but effective therapy should be con-sidered in the limited number of patients where the likelihoodof exchange transfusion is greatest. These would includeneonates with red cell alloimmunisation unmodified byantenatal therapy or neonates with potential ABO HDNwhere a previous sibling has suffered from severe diseaserequiring exchange transfusion. Also the neonate with severeDAT-positive hyperbilirubinaemia readmitted from the com-munity, where the serum bilirubin already exceeds localguidelines for exchange transfusion, but where initial therapywith IVIG is liable to be available more quickly than exchangetransfusion. In these relatively rare circumstances adjuvanttherapy with IVIG seems justified. A single dose of IVIG of500 mg/kg appears to be as effective as any other regimen.
521
haemolytic disease) with moderate hyperbilirubinaemia(plasma bilirubin 256308 mmol/L) developing between 4896 h of age. Despite being a population of relativelyuncomplicated neonates a significant number of these wouldbe expected to go on to be treated with phototherapy, oftencausing maternal anxiety and lengthening hospital stay. Thestudy enrolled a total of 84 neonates, 40 of who received asingle intramuscular dose of SnMp at 6 mg/kg body weight. Inthe control neonates 12 (27%) required phototherapy at a pre-
determined level of 333 mmol/L, whereas none of the SnMptreated neonates required phototherapy. SnMp treated neo-nates also required a shorter period of plasma bilirubinmonitoring and a reduced number of plasma bilirubinmeasurements. No adverse effects of SnMp use were observed.
Positive effects of SnMP in reducing peak plasma bilirubinconcentrations have also been observed in neonates withglucose-6-phosphate dehydrogenase deficiency [55]. Inaddition neonates of Jehovah's Witness parents have beengiven SnMP to reduce the likelihood of jaundiced neonatesrequiring therapy with exchange transfusion [56]. Given these data there is good evidence to suggest that asingle dose of SnMP in uncomplicated neonates reduces peakplasma bilirubin concentrations and reduces the need forphototherapy. As these are outcomes that themselves are notlikely to result in harm it can be argued that SnMP therapy
presents an unknown risk as the long-term consequences ofsuch therapy are not yet fully known. However, phototherapyin relatively well neonates often provokes a high degree ofmaternal concern and prolongs hospital stay, both of whichare unwanted outcomes in modern hospital-based medicalpractice. Further studies are underway to more fully assessthe efficacy and safety of SnMP but the use of metallopor-phyrins to reduce the medical burden of neonatal hyperbilir-ubinaemia may well find a role in the future as models ofhealth care become increasingly community centred.
14.3. Metalloporphyrins
Metalloporphyrins are heme analogs that competitivelyinhibit the activity of heme oxygenase, the rate-limitingenzyme in heme catabolism. This action reduces theformation of bilirubin and makes them potential agents forboth the prophylactic and therapeutic reduction of hyperbi-lirubinaemia in the newborn. Tin (Sn) mesoporphyrins are themost fully studied compounds in this context. In 1988 Kappaset al. [52] reported the prophylactic use of Sn-Protopor-phyrin (SnPP) in 122 term infants with DAT-positive ABOincompatability. At doses up to 2.25 mg/kg body weight,
administered by 2 or 3 intramuscular injections, theydemonstrated a significant reduction in the rate of rise ofplasma bilirubin levels beginning at 48 h post SnPP admin-istration that continued until 96 h. The only reported sideeffect in SnPP treated neonates was transient erythemaduring the concurrent use of phototherapy in two neonates.
In 1994 Valaes et al. [53]. reported the results of 5sequential studies of the prophylactic use of Sn-Mesopor-phyrin (SnMp) in preterm neonates between 30 and 36 weeksgestational age. SnMp was administered at doses up to 6 mg/kg body weight by intramuscular injection beginning withinthe first 24 h of life. 517 neonates were studied over 4 yearsbetween 1988 and 1992. As the study population werepreterm newborns prophylactic phototherapy was com-menced at predetermined low levels and the main outcomeof the study was a reduction in the requirement for
phototherapy in SnMp treated neonates. This was mostmarked in those neonates receiving the highest dose of Sn-Mp (6 mg/kg) where mean peak incremental plasma bilirubinconcentration was reduced by 41% and phototherapy require-ments by 76%, compared to control neonates. Transienterythema was again noted in conjunction with phototherapyin SnMp treated neonates but no other adverse effects werenoted during the study or at follow-up at 3 and 18 months.
More recently Martinez et al. [54] have looked at thetherapeutic effect of SnMp in healthy term neonates (without
15. Practice points
The diagnosis, acute management and follow-up ofneonates with HDN still represent a significant area ofactivity for maternity/neonatal services.
ABO incompatability is now the single largest cause ofHDN in the western world.
As the efficacy of phototherapy increases the role ofexchange transfusion in the acute management of HDN israpidly decreasing.
With increasing knowledge at the molecular level, andcloser liaison between neonatal paediatricians andhaematologists, the diagnosis of non-immune causes ofHDN is increasing. As these conditions have an inherited
basis and therefore have implications for other familymembers (or future children), it is a high priority for allneonatal paediatricians to achieve an accurate diagnosisin all cases of HDN.
All neonates with persistent haemolysis should always befully investigated and followed up and appropriately.
16. Research directions
Although difficult to achieve, evidence-based guidelines forindications for exchange transfusion in the post-RhD HDNera are required.
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Maternal sensitization to red cell allo-antigens remains asignificant cause of HDN. Further studies aimed at investi-gating the causes of, and ways to reduce, such sensitizationare necessary.
The ease of delivery of phototherapy will always meanthat further research to advance it's effectiveness in thetreatment of HDN is worthwhile.
IVIG and IM metalloporphyrins appear to reduce the needfor exchange transfusion in neonates with hyperbilirubinae-
mia. Both are readily available and easy to administer (asapposed to blood for, and the process of, exchange transfu-sion). Further trials to define optimal patient populations anddoses are required.
I.A.G. Roberts
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