1275

INTERVAL FROM CUSUM CHANGE TO DATE OF CONFIRMED

RELAPSE IN 18 CHILDREN WITH ALL

*No difference in cases E and K—N.tNo cusum change in cases O-RCCR = continuous complete remission; PB = peripheral blood.

detected in only 5 of the 8 patients who relapsed after the end oftreatment.

Cusum analysis of Hb and WBC and platelet counts extractsinformation from the blood-count not seen by scrutinising orplotting individual results. The method amplifies the small changesin blood-count data that occur before obvious cytopenias developand enable early trends in blood-count to be detected against anoften abnormal background. Changes in the cusum for Hb andWBC and platelet counts will also indicate changes in the peripheralblood-count which may have occurred for reasons other than

relapse. There were 9 episodes where a cusum change wasimmediately followed by bone-marrow aspiration. These aspiratesconfirmed that treatment had been responsible for the change ratherthan relapse. Cusum analysis cannot discriminate betweentreatment effect and relapse. It can, however, allow more sensitivemonitoring of Hb, WBC, and platelets, and provide an objectiveindication for bone-marrow aspiration. Haematologists might find asimilar approach useful in monitoring blood-data.

Department of Haematology,University of Wales College of Medicine,Heath Park, Cardiff CF4 4XN

G. J. MORGANS. THOMASI. CAVILL

D. P. BENTLEY

1. Haworth C, Hepplestone AD, Morns-Jones PH, Campbell RHA, Evans DIK,Palmer MK. Routine bone marrow examination in the management of ALL ofchildhood. J Clin Pathol 1981; 3: 483-85.

2. Watson DK, Robinson AE, Bailey CC. A reappraisal of routine marrow examinationin the therapy of ALL. Arch Dis Child 1981; 56: 392-404.

3 Komp DM, Fischer DB, Sabio H, McIntosh S. Frequency of bone marrow aspiratesto monitor ALL in childhood. J Pediatr 1983; 192: 395-97

4 British Standard Institute BS 5703, 1980 part 1 and 2.5 Chaput de Samtonge DM, Vere DW. Why don’t doctors use cusums. Lancet 1974, i:

120-21.6 Freedman L. Cusums. Lancet 1974, i 741-42.

SAFETY OF EQUINE RABIES IMMUNE GLOBULIN

SIR,-Human rabies immune globulin (HRIG) is the product ofchoice for early passive protection of patients exposed to rabies.1-3However, few patients in countries where rabies is still a majorpublic health problem can afford it. In Thailand, for example, over100 000 individuals are given post-exposure rabies treatment everyyear, and 250-300 deaths are reported. HRIG costs$285, or theequivalent of at least 100 days wages for an average Thai labourer.The same man would have to work for only 9 days to pay forpurified equine rabies immune globulin (ERIG). Most patientstreated for rabies exposure in Thailand still receive vaccine alone,

and if immune globulin is administered it is almost always of equineorigin. Our institution treats 1200-1400 such patients every month:more than 95 % now receive a tissue culture vaccine ’Verorab-

TRC’) and 30% or so are also given immune globulin; (ERIG in95% and HRIG in 5% of cases).Our staff have long had the impression that the rate of local and

systemic immediate or delayed serum sickness reactions is low.None could remember an anaphylactic reaction, and they couldrecall only 1 patient in the past year who required a short course ofsteroids for serum sickness. This is in sharp contrast to warnings intextbooksm3 of a 20-50% frequency of serum sickness when ERIGis used. We decided to study 500 successive Thai patients whorequired rabies immune globulin. 278 were male and 222 female;ages ranged from 1 to 84 years. All patients were followed up for amonth or more after the injection of Pasteur Vaccins ERIG (8 weregiven the Swiss Serum and Vaccine Institute’s product instead).

All patients were skin tested by the intradermal administration ofERIG in a 1 in 10 dilution, raising a bleb 3 mm in diameter. Skintests were read independently by two staff members. Any wheal orflare greater than 5 mm was considered positive. There were nountoward reactions to the skin test. All 59 patients with a positiveskin test were offered HRIG, but only 15 could afford it, the other44 being given ERIG under close observation and after oraladministration of antihistamines. 22 of these 44 had a wheal and/orflare greater than 10 mm. None of them had any immediate local or

systemic symptoms or delayed serum-sickness-like reactions.Only 4 of the 485 patients given ERIG had any delayed type

hypersensitivity reactions, and none of the 4 had had a positive skintest. In these 4 women aged 20, 25, 37, and 52 symptoms appeared6, 7, 10, and 12 days after ERIG was given. The symptoms werefever (2), discomfort at the injection site (2), arthralgia (1), urticaria(1), and a generalised erythematous rash (3). The only treatmentwas an oral antihistamine and all 4 patients recovered fully within aweek.We conclude that ERIG (Pasteur Vaccins) is a safe product and

has an adverse reaction rate of less than 1 % in Thai patients given40 IU/kg as an intramuscular and bite-site injection. Our previousexperience with Swiss ERIG leads us to believe that it is equallysafe.

Science Division,Thai Red Cross Society,Queen Saovabha Memorial Institute,Bangkok 10500, Thailand

HENRY WILDEPRANEE CHOMCHEYSOMPOB PRAKONGSRIPOR PUNYARATABANDHU

1. Kaplan C, Tunes GS, Warrell DA. Rabies. the facts. Oxford Oxford UniversityPress, 1986. 64.

2 Corey L. Rabies. In: Harrison’s principles of internal medicine. New York:

McGraw-Hill, 1987;714.3. Baer GM. In: Kurstake’s control of virus diseases. New York: Marcel Dekker, 1984:

86

DNA PROBES WHICH UNAMBIGUOUSLYDISTINGUISH TAENIA SOLIUM FROM T SAGINATA

SIR,--Clinicians want a diagnostic test that distinguishesinfestations with the "pig" tapeworm Taenia solium from those withthe "beef ’ tapeworm T saginata.1 Both species are highlyhost-specific in that the adult worm occurs only in the smallintestine of man. However, in contrast to T saginata, eggs ofT solium can also develop in man to the cysticercus or larval stage.This can lead to serious and often fatal disease (cysticercosis) due tothe frequent involvement of the central nervous system.2 In chroniccases (neurocysticercosis), larvae lodge in the brain, often causingepilepsy and death.2The difficulties in distinguishing members of the taeniid group of

cestodes are well recognised.3 Morphological procedures are

imperfect for human taeniids because the scolex is rarely voided andthe diagnosis has to rely on one or a few expelled proglottids whichmay be poorly preserved. When suspected cases have been treated(eg, with praziquantel) morphological characters such as thestructure of the ovary and the number of uterine branches are likelyto be unreliable. Inter-species differences can be detected

biochemically (eg, by electrophoresis of total proteins° and enzymeelectrophoresis5,6). The electrophoretic patterns are difficult tointerpret, and the parasite material has to be immediately processed