laboratory investigations

1

LABORATORY INVESTIGATIONS

SAURABH ROY

24.08.2015

2Contents:1. Need for Lab investigations2. Definition3. Generic Applications4. Classifications5. Crucial Q&As prior to Lab Investigations6. Laboratory Investigations(Frequently and infrequently required)

a. Haematological Investigationsb. Biochemistry Investigations

3Contents:c. Microbiological Investigationsd. Immunological Investigationse. Histopathological and Cytopathological Investigations

7. Common Clinical Scenarios8. Conclusion9. References

4Need for:Evidence shows Case History and Clinical examination usually

reveal most if not all of clinically relevant dataHence there remains a need to confirm our clinical impressionLab investigations supplement rather than replace other methods

for gathering information It is a known fact that with the help of lab investigations, some

underlying systemic conditions of which the patients are unaware of, are often identified in dental practice for the first time

5Definition:Laboratory studies are an extension of physical

examination in which tissue, blood, urine or other specimens are obtained from patients and subjected to microscopic, biochemical, microbiological or immunological examination.

Information obtained from these investigations help us in identifying the nature of the disease.

6Generic Applications:Confirming or rejecting clinical diagnosisProviding suitable guidelines in patient managementProviding prognostic information of the diseases under

considerationDetecting diseases through case-finding screening methodsEstablishing normal baseline values before treatmentMonitoring follow up therapyProviding information for Medico-Legal consultations

7Classifications:Based on where investigation is done:

Chair side Investigations

Laboratory Investigations

Acts as a precursor to laboratory investigations

Significantly higher sensitivity and specificity

Egs : Toluidine blue staining for grading dysplasia, Electric Pulp testing for tooth vitality, Radiographs

Egs: Glycated Haemoglobin estimation,Peripheral smear histology

8Classifications:Based on specificity/sensitivity:

Screening Tests Diagnostic TestsAn ideal screening test is 100% sensitive

An ideal diagnostic test is 100% specific

Useful in a large sample size at risk; typically cheaper

Useful in symptomatic individuals to establish diagnosis or asymptomatic individuals with +ve screening test; expensive

Egs : blood glucose estimation for screening diabetes,Haematocrit values for anaemia,VDRL test for syphilis

Egs: Glycated Haemoglobin estimation, OGTTPeripheral smear histology,FTA-Abs test for syphilis

9Classifications:Based on Hospital Lab Services:

Haematology

Microbiology

Biochemistry

Immunology

10Haematology:Deals with investigations of abnormalities of blood cells, their

precursors and of the haemostatic & clotting mechanisms

Microbiology: In this discipline body fluids, mucosal surfaces and excised

tissues are examined by using microscopical, cultural and serological techniques.

To detect and identify the causative micro organism Eg: Antibiotic sensitivity testing

11Biochemistry:Also called chemical pathologyDeals with investigations of the metabolic

abnormalities of the body in disease states. Investigations are carried out by assays of various

normal and abnormal compounds found in body fluids viz. blood, urine, CSF, saliva etc.

12Immunology:Deals with the detection of abnormalities in the

immune systemPrimary role to Identify a disease is by observing

the presence of an antibody in the patient that resulted from the infection(entry of pathogen)

The semi quantitative measure of the amount of antibody present in serum is called a Titre.

13Histopathology: Deals with the identification of structural changes in diseased

tissues through microscopic examination of appropriately stained tissue sections obtained from biopsy procedures.

Cytopathology:Scientific Study of role of individual cells or cell types in disease.Clinician collects a sample of abnormal cells from lesional tissue scrapings

or by means of tissue aspiration.Cells are then stained and studied under light microscopy

14Classifications:Based on frequency of dental use: (by Sonis, Fazio & Fang )

Frequently used:• CBC- Hb, Hct,

Absolute and differential WBC

• Bleeding studies – BT,CT, PT, aPTT

• Peripheral Blood Smear

• Random Blood Glucose

Occasionally done:• Tests for disturbance

of bone – Ca, P, ALP• ESR• Urinalysis• Screening Test for

Syphilis

Rarely ordered:• Enzyme testing –

CPK, SGOT, SGPT, LDH

• Bilirubin Estimation• Creatinine

Estimation• Acid Phosphatase• BUN

15Crucial Q & As prior to Lab Investigations:1. For a given situation, WHAT investigation is appropriate? Often a dental practitioner is faced with a dilemma of what investigation to

order in a given clinical scenario. The plan of investigation should be therefore decided from the facts

obtained from history taking and clinical examination Investigations are useful only when the appropriate tests are requested, and

interpreted in the light of history, clinical findings, knowledge and experience.

Before any investigations are initiated, Patient Consent must be obtained

16Crucial Q & As prior to Lab Investigations:2. What sample to be collected for the Test? Samples should optimally be the most likely entity which harbours the

causative organism or abnormal constituents of body fluids like electrolytes, chemical compounds or antigens

17Crucial Q & As prior to Lab Investigations:3. How to collect specimens? Success or failure of the investigation depends on the procedures carried

out in collection, preservation and transport of the specimens. In cases of microbiological and culture tests, the specimen must be material

from the actual site of infection and should be collected with minimum of contamination from adjacent tissues or secretions.

In cases of tissue collection, the site of collection as well as the vicinity with respect to the lesion assumes importance

Apart from this the timing (When??) of specimen collection is also important

18Crucial Q & As prior to Lab Investigations:3. How to collect specimens? In general specimens collected from swabs are inferior in material

collection when compared to aspirates. In cases of collection of blood samples for haematology, it can be collected

either via skin , venous or arterial puncture If a clinician wishes to study its cellular components, its important that the

blood sample remain unclotted. If blood specimen has been refrigerated, it must be brought back to room

temperature for investigations as cold specimens yield false values.

19Crucial Q & As prior to Lab Investigations:4. What Information to be furnished to the laboratory? Specimens should accompany properly filled out forms from the clinician Preliminary details include: Name, Address, Hosp. No. , Gender & Date of Birth Other important details are

Exact nature of the specimen Source of the specimen Nature of investigation requested Date and time of specimen collection Brief Clinical Details Tentative Diagnosis Current Therapy if any

20Crucial Q & As prior to Lab Investigations:5. Estimated cost and time expense? The clinician should comprehensively detail the patient about the cost

aspect of the following investigation in order to allow the patient to make an informed choice of undertaking it.

The clinician should also provide a realistic estimate of the time duration required from the collection of specimen from patient till obtaining the results and its interpretation

21Crucial Q & As prior to Lab Investigations:6. Expected risks and discomfort to patient, clinician and personnel? The patient must be beforehand explained about the possible risks of the

investigative procedure, if any Verbal informed consent is adequate for non invasive procedures, but for

invasive procedures a signed, witnessed and a written informed consent is necessary.

All body fluids and tissues are considered potentially infectious. Barrier precautions must always be employed to prevent transmission to

other patients or staff during investigations.

22Crucial Q & As prior to Lab Investigations:7. Interpretation of results? Clinician’s knowledge of pathology is essential for interpreting results. The clinician should be able to assess the false negative results in non-

quantitative tests For quantitative tests, the normal values may vary between different lab

settings. Hence communication with laboratory personnel becomes very important in these settings.

It must also be remembered that a value just outside the range of normal does not necessarily indicate abnormality.

23Lab Investigations(Frequently and infrequently required):

24Haematological Investigations(Frequently used) :

Complete Blood count includes:1. Hb2. PCV3. RBC Count4. TLC5. DLC6. Platelet count7. ESR8. RBC Indices

25Haematological Investigations: RBC Count:

Normal range – Adult male : 4 - 6 million cells/cu. mm

Adult female : 3 - 5 million cells/cu. mm

Polycythaemia Anaemia

Abnormally high values of circulating RBCs; may be primary or secondary

Abnormally low values of circulating RBCs

Seen in abnormality of bone marrow(primary) or altitude related(secondary)

May result from chronic haemorrhage, bone marrow failure(secondary to radiation, drugs or tumour associated)

26Haematological Investigations: Haematocrit (Hct) :

Volume of packed erythrocytes/100ml of blood done in a centrifugeAlthough test is inaccurate, it is more precise than the erythrocyte count

and is used in combination with itNormal range: Adult male : 40-54%

Adult female : 38-47% In general these values are increased in polycythaemia and reduced in

anaemia.

27Haematological Investigations: Haemoglobin(Hb) :

Oxygen carrying component of erythrocytesHence, amount of Hb in the RBCs indicates the level at which it can

supply oxygen to the tissuesNormal range – Adult male : 14 -18 g%

Adult female : 12 – 16 g%Low values indicate anaemia while high values indicate

polycythaemia

28Haematological Investigations: Peripheral Smear:

Provides info concerning the size and shape of the red blood cellsIt may allow

Identification of sickle cell & normocytic, microcytic and macrocytic anaemia

Evaluation of Hb pigmentation of individual cells to be classified as normochromic, hypochromic or hyper chromic

29Haematological Investigations: Mean Cell Volume(MCV):

Ratio of Haematocrit to RBC count expressed in µm3.Describes volume of RBC range:

Normal – 82-92/ µm3

Normocytic anaemia – 82-92/ µm3

Microcytic anaemia – 50-80/ µm3

Macrocytic anaemia – 95-100/ µm3

30Haematological Investigations: Mean Cell Haemoglobin(MCH):

Ratio of Hb to RBCs and is expressed in picograms It expresses the Hb component of each cell range:

Normal – 27-31 pcgNormocytic anaemia – 25-30 pcgMicrocytic anaemia - 15-25 pcgMacrocytic anaemia - 30-50 pcg

31Haematological Investigations: Mean Cell Haemoglobin Concentration(MCHC):

Ratio of Hb to HctValue expressed as a percentage of volume of red blood cells.Measures Hb concentration in grams/100ml of packed erythrocytes range:

Normal – 32-36% Normocytic anaemia – 32-36% Microcytic anaemia - 25-30% Macrocytic anaemia - 32-36%

32Haematological Investigations: Erythrocyte Sedimentation Rate(ESR or Sed Rate):

In certain febrile diseases as well as in others the amount of circulating fibrinogen is increased

The resultant increased viscosity of blood slows down the sedimentation rate of erythrocytes

ESR indicates the speed with which the erythrocytes settle in uncoagulated blood

Values: Men < 50 years - <15 mm/hr. Women < 50 years - <20 mm/hr. Men >50 years - <20 mm/hr. Women >50 years - <30 mm/hr.

33Haematological Investigations: Erythrocyte Sedimentation Rate(ESR or Sed Rate):

Interpretation:

Raised ESR Lowered ESRTuberculosis Polycythaemia

SABE Spherocytosis

Acute MI Sickle Cell Anaemia

Septic Shock Congestive Heart Failure

Anaemia New Born Infant

34Haematological Investigations: White Blood Cell Count: (WBC)

The white blood cells or Leukocytes are classified as either granulocytes or agranulocytes

Normal range: 4500-11000 cells/mm3

High values may be caused by leukaemia, polycythaemia or infectious diseases

Low values may be due to bone marrow depression, aplastic anaemia, drug reactions and viral infections viz influenza

35Haematological Investigations: Differential White Blood Cell Count: (DLC)

Obtained from a peripheral blood smearThe granular and nongranular leukocytes are counted and its

values are expressed as a percentage of Total WBCNeutrophils:

Band neutrophils are immature while seg neutrophils are matureNormal Band value – 2-3% while normal seg value – 50-60%High Band value may indicate presence of an acute infection while Low

value may indicate bone marrow depressionHigh Seg values may indicate AML, drug/poison intoxication while Low

value may indicate malignant neutropenia or aplastic anaemia


Basophils:Normal value – 0 – 1%High values uncommon; may indicate myeloproliferative diseaseLow values may indicate an oncoming anaphylactic reaction

Eosinophils:Normal value – 0 – 5%High values are mostly observed in allergies or parasitic infectionsLow values are mostly observed in aplastic anaemia and patients on

cortisone therapy


Lymphocytes:Normal value – 30 – 40%High values may indicate chronic/viral infections, lymphocytic leukaemiaLow values may indicate aplastic anaemia or myelogenous leukaemia

Monocytes:Normal value – 3 – 7%High values are seen in Monocytic leukaemia, Hodgkin’s disease, SABELow values are mostly seen in aplastic anaemia

38Haematological Investigations:Bleeding Time:

Measures the time for haemostatic plug formationNormal Bleeding time – 2-7 minsAny clotting factor deficiency or platelet abnormality will lead to increased BTProlonged in

ThrombocytopeniaAcute leukaemiaAplastic anaemiaLiver diseasesVon-Willebrand’s disease

39Haematological Investigations:

Clotting Time:Measures the time required for formation of first clot.Screening test for coagulation disordersNormal Clotting time – 4-14 mins

40Haematological Investigations(infrequently required) :

1. Prothrombin Time (PT):Time in seconds that is required that is required for fibrin threads to form in citrated or

oxalated plasmaNormal time – 11-14 secsMeasured against a Control PT in terms of INRINR = PTTest / PTNormal

Normal INR = 1 ; Abnormal INR > 1.5Measures extrinsic and common pathway – Factors I,II, V ,VII, X


1. Prothrombin Time (PT):Increased PT

Disseminated Intravascular CoagulationPatients on Warfarin TherapyVit K deficiencyEarly & End stage Liver failure


2. Activated Partial Thromboplastin Time (aPTT): Time in seconds that’s required for a clot to form in citrated or oxalated plasmaPerformance indicator of both the intrinsic & common pathwaysTypical reference range – 30-40 secs Increased aPTT seen in :

Patients on Heparin TherapyVon – Willebrand’s diseaseDisseminated Intravascular CoagulationEarly Stage Liver failure/ Wilson’s diseaseHaemophilia


3. Rumpel-Leede Test(Tourniquet Test):Test of ability of the superficial capillaries of the skin of the forearm and hand to withstand

an increased intraluminal pressure and a certain degree of hypoxiaDone by occluding veins of the upper arm with a blood pressure cuff for 5 mins.Indicated in suspicions of bleeding abnormalities, petechiae in oral cavity and scurvyPresence of >20 petechiae/sq. inch is considered abnormalDental Application – screening test for scurvy (Scorbutic gingivitis)


4. Schilling Test:It is a measure of the patient’s ability to absorb orally administered radioactive Vit B12

labelled with 60CoPatients with pernicious anaemia excrete less than 5% of orally administered dose in

comparison with 8-25% by normal individuals


5. Serum Iron and Total Iron Binding Capacity: Iron deficiency is usually detected on the basis of the amount of iron

bound to transferrin in the plasma(serum iron) and the total amount of iron that can be bound to the plasma transferrin in vitro

Normal values Serum iron – 80-180 µg/dlTIBC – 250 – 370 µg/dl

47BioChemistry:

48Serum chemistry:Serum is that portion of blood remaining after whole blood has been

allowed to clotResponsible for fluid maintenance Intra and extra cellularlyResponsible for the optimal osmotic gradient, nerve and muscle

function and hydration

49Serum chemistry(frequently used):

1. Blood Glucose estimations: Fasting Blood Sugar(FBS): Normal values – 70-90 mg/100mlRandom Blood Sugar(RBS): 110-130 mg/100mlPost Prandial Blood Sugar(PPBS): <140 mg/100mlHigh values are seen in Diabetes mellitus, Cushing’s disease,

pheochromocytoma, in patients taking corticosteroidsLow values seen in insulin secreting tumours, Addison’s, Pituitary hypo

function

50Serum chemistry(frequently used):

2. Oral Glucose Tolerance Test:2. Used for the definitive diagnosis of diabetes mellitus and for

distinguishing diabetes from other causes of hyperglycaemia like hyperthyroidism

3. Should be performed on only healthy ambulatory patients who are not under any drugs which may interfere with glucose estimation

4. Oral Glucose Challenge: explain5. OGCT(challenge Test) is a short version of OGTT used in pregnant

women to check for Gestational Diabetes

51Serum chemistry(frequently used):Oral Glucose Tolerance Test:

Criteria for Interpretation:

1. Fajans and Conn Criteria

2. Wilkerson Point System

3. The University Group Diabetes Program Criteria

52Serum chemistry(frequently used):Oral Glucose Tolerance Test:Fajans & Conn Criteria:

Abnormally increased values of any 2 parameters indicate diabetesFasting Blood Sugar > 100 mg/dl1 hr. BS > 160 mg/dl2 hr. BS > 120 mg/dl


Wilkerson Point System:A score of 2 or more indicates diabetesFBS > 110 mg/dl - 1 Point1 hour > 170 mg/dl – 0.5 point2 hour > 120 mg/dl – 0.5 point3 hour > 110 mg/dl – 1 point


University Group Diabetes Program Criteria:Based on the sum of 1,2 and 3 hr. levels of Blood sugarIf sum >/= 500 mg/dl a diagnosis of diabetes is made

55Serum chemistry(frequently used):3. Glycated Haemoglobin(HbA1c):Hb becomes Glycated by ketoamine reactions between glucose and

other sugars.Once Hb is Glycated, it remains that way for a prolonged period(2-3

months)Hence it provides a definitive value of blood sugar control of 2-3 month

durationThe HbA1c fraction is abnormally elevated in diabetic patients with

chronic hyperglycaemiaIt is considered to be a better indicator for diabetic control compared to

blood glucose levels

56Serum chemistry(frequently used):Glycated Haemoglobin(HbA1c):Range:

57Serum chemistry(infrequently used):

1. Serum Calcium, Phosphorus: Indicated on suspicion of Paget’s disease, fibrous dysplasia, primary and

secondary hyperparathyroidism, osteoporosis, multiple myeloma or osteosarcoma

The concn. Of Serum Ca varies inversely with serum P Normal level Serum Ca – 9.2-11 mg/dl Normal level Serum P – 3- 4.5 mg/dl At levels less than 7 mg/dl Serum Ca, signs of tetany may appear

58Serum chemistry(infrequently used):2. Serum Alkaline Phosphatase: (ALP) ALP produced in small amounts in the liver but most notably in

osteoblasts Normal values:

ADULT CHILD

King Armstrong Units 4-13 15-30

Bodansky Units 1.5-4.5 5-14

International Units(IU/l)

30-85


2. Serum Alkaline Phosphatase: (ALP)High values Low values

Obstructive liver disease HypophosphatasiaPaget’s disease of bone HypothyroidismOsteomalacia OsteoporosisRickets Aplastic/Pernicious

anaemiaSarcoidosis Chronic Myeloid

LeukaemiaLymphoma Wilson’s Disease


2. Serum Alkaline Phosphatase: (ALP) This test is very useful for diagnosing biliary obstruction. Even in mild cases of obstructive disease, this enzyme is elevated. It is not very useful for diagnosing cirrhosis. If a patient has bone disease, this test may be highly inaccurate, as ALP is

also found in bone tissue.


3. Serum Uric Acid: End product of purine metabolism Normal values:

Males : 2.1-7.8 mg/100ml Females : 2.0-6.4 mg/100ml

Abnormally high uric acid level seen in Gout, Renal failure, leukaemia, lymphoma, starvation , lead poisoning & cancer chemotherapy

Low values are rare


4. Serum Creatinine: Metabolic product of dephosphorylation of creatinine phosphate Raised in late stage Renal disease Its analysis is preferred to Serum Urea analysis as dietary protein intake

and protein catabolism do not alter its levels in the body Levels > 15 mg/dL indicates impaired renal metabolism

63Serum chemistry(infrequently used):5. Blood Urea Nitrogen: Formed by the deamination of amino acids in the liver Protein metabolism produces ammonia, a toxic substance that is

converted into urea. Normal values – 8 -18 mg/100ml

High BUN readings are seen in acute or chronic renal failure, congestive heart failure and urinary tract obstructions


6. Total Protein & Albumin/Globulin Ratio: These proteins are important in coagulation, transport a variety of

hormones, act as buffer systems and help maintain osmotic pressure Normal range:

Total protein – 6 – 8.3 g/dL A/G ratio - 1.2 – 2.0


6. Total Protein & Albumin/Globulin Ratio:High Total Protein values

Low Total Protein Values

Lupus erythematosus Inadequate Protein Intake

Collagen diseases Protein Malabsorption

Acute liver diseases Diarrhoea

Multiple Myeloma Anaemia & Burns


7. Serum Bilirubin: (Brb) Bilirubin is a bile pigment derived from the breakdown of Haemoglobin Normal value: 0.1 – 1.2 mg/100ml Levels beyond 3.0 mg/100ml may indicate jaundice High values may also indicate haemolytic anaemia, biliary obstruction,

hepatitis and Gilbert’s disease

67Serum chemistry(infrequently used):8. LDH,SGOT,SGPT: LDH is responsible for the oxidation of lactic acid to pyruvic acid

Normal range: 71-207 IU/L SGOT(AST) is responsible for conversion of amino acids to keto acids

Normal range: 0-35 IU/L SGPT(ALT) is responsible for diagnosis of liver functions more so than

SGOT levels Normal range: 0-35 IU/L

68Serum chemistry(infrequently used):8. LDH,SGOT,SGPT: These enzymes can be indicative of liver disease. However, these enzymes are also found in other body tissues such as

bone, heart, kidney, etc. Isoenzyme tests usually must be performed in order to isolate the

isoenzyme that is elevated and if the source is the liver.

69Serum chemistry(infrequently used):9. Blood Electrolytes: An automated analysis usually includes Sodium(Na), Potassium(K),

chloride(Cl) and Bicarbonates(HCO3- )

Normal values:Sodium 136-145 mEq/L

Potassium 3.8-5.5 mEq/L

Chloride 95-105 mEq/L

Bicarbonates 22-28 mEq/L

70Serum chemistry(infrequently used):10. Serum Protein Electrophoresis: By this technique albumin and fibrinogen may be separated from

globulin, with globulins further separated into 4 major groups:I. Alpha-1II. Alpha-2III. BetaIV. Gamma

71Serum chemistry(infrequently used):10. Serum Protein Electrophoresis: In dental practice it is recommended that this procedure be carried out

I. To rule out the presence of multiple myelomaII. Patients with radiolucent defects detected in radiographic examination of

cranium and jaws(esp. when pulpal or periodontal foci cannot be evidenced)

III. Patients with atypical facial neuralgia

72Saliva Chemistry(infrequently done): Secretions are collected directly from individual parotid and submandibular &

sublingual glands by use of small rubber cups(Curby cups) pressed lightly against gland orifices

Salivary function studies include:1. Measurement of Na, K, Cl concentration in saliva

2. Measurement of total salivary flow

3. Rate of flow of saliva from orifices

4. Rate of discharge of radio-opaque dye from salivary gland following retrograde sialography

5. Rate of uptake and secretion of 99m Tc-pertechnate by salivary glands

73Saliva Chemistry: Normal values for unstimulated saliva are

K – 25 mEq/LNa - <10 mEq/LCl - 15-18 mEq/L

Increase in K or Na values may indicate generic inflammation or sialodenosis

In parotid enlargement accompanying cirrhosis Parotid flow rate and salivary concn of Na,K,Cl, salivary amylase & protein increases Immunoglobulin levels remain normal

74Saliva Chemistry: In Sjogren’s Syndrome

Flow rate is reducedSalivary phosphate concn is reducedNa & Cl concn is elevatedSalivary IgA concn elevatedUrea and K concn unchangedAbnormal protein bands can be distinguished by electrophoresis

76Microbiology:

77Microbiology: Culture and sensitivity tests are used to isolate and identify causative micro

organisms of an infection May be obtained from blood or urine Particularly helpful in evaluating infections related to throat, sinuses, root

canals or bone. Sensitivity tests may also be ordered when patient relapses, the

identification of the organism is uncertain or the disease is severe Most common limitation is the delay in receiving the report Another problem is in-vitro testing may not necessarily predict the same

result as in-vivo testing

79Immunology:

80Immunofluorescence Procedure: This procedure employs the use of fluorescent labelled antibodies to

detect specific Ag-Ab reaction of known specificity in tissue sections When tissue sections labelled in this fashion are illuminated with ultra

violet light in an UV microscope, specific labelled tissue component can be identified by their bright apple green fluorescence against a dark background

81Immunofluorescence Procedure:

Direct Immunofluorescence• Addition of fluorescent

labelled Ab to patient tissue

• Wash• Visualizing under

fluorescent microscope

Indirect Immunofluorescence• Addition of patient serum

to tissue containing known Ag

• Wash• Add fluorescent labelled

Anti globulin• Wash• Visualize

Sandwich Technique• Refers to the fact that the

Ag is sandwiched between 2 layers of Ab only one of which is labelled

• Incubation and washing• Labelled antiserum is

applied to the section which identifies location of tissue component

82Immunofluorescence Procedure:

83Immunology(Infrequently used methods):1. ImmunoPrecipitation Assays:

Detects Antibody in solution End point is visual flocculation of the antigen and the antibody in

suspension

2. Complement Fixation: Based on activation/fixation of complement following binding of

complement factors to Ag-Ab immune complexes

84Immunology(Infrequently used methods):3. Particle Agglutination:

Relatively simple and fast Capable of detecting lower concentration of antibodies Designed to detect antibodies to viruses, subsequent to vaccination Utilizes Ag coated latex particles, coal particles

85Immunology(Infrequently used methods):4. Enzyme Immuno Assay:

Most sensitive Usually indirect assay that depends on the use of anti human IgG or IgM Ab

conjugate Antibody conjugate, if present is made to attach to enzyme which catalyses

conversion of substrate to a coloured product which is then read by a spectrophotometer

86Immunology(Infrequently used methods):5. Radio Immuno Assay: Extremely sensitive and specific procedure Used to measure concentration of Ag in patient’s sera by using Ab To perform this, a known quantity of Ag is made Radioactive and is made

to compete with Ag in patient’s sera for Ab binding sites The radioactivity of free Ag remaining is measured using a Gamma

counter

87Histopathology and Cytopathology:

88Histopathology and Cytopathology:

Histopathology refers to the microscopic examination of tissue in order to study the manifestations of the disease

Cytopathology refers to the scientific study of role of individual cells or cell types in disease

89Tissue Biopsy: A biopsy is a controlled & deliberate removal of tissue from a living organism for

the purpose of microscopic examination Relatively simple procedure producing little discomfort when compared to

exodontia or periodontal surgery Indications:

When signs and symptoms of an observed tissue change do not provide enough information to make a diagnosis

When neoplasia is one of the differential diagnosisTo confirm a clinical diagnosis

90Tissue Biopsy: Contraindications:

The systemic health of the patient may contraindicate biopsy completely or at least cause its postponement

Site of the lesion may pose a risk to biopsy (for eg. Biopsy in richly vascularized areas may pose a risk of haemorrhage)

Cases of clinically obvious malignant neoplasm should be referred directly to the appropriate specialist as biopsy would delay definitive care rather than accelerate it

91Tissue Biopsy: Avoidance of Delay for Biopsy:1. Rapid growth2. Absent local factors3. Fixed lymph node enlargement4. Root resorption with loosening of teeth5. History of malignancy

92Tissue Biopsy: Uses:1. Diagnosis2. Grading of tumours3. Metastatic lesions4. Recurrence5. Management Assessment

93Tissue Biopsy Types:

Excisional biopsy:

Total excision of a small lesion for microscopic exam.Diagnostic + Therapeutic

Incisional Biopsy

Performed by removing a wedge shaped specimen of pathological tissue along with surrounding normal zone

Punch Biopsy:With this technique the surgical defect produced is small and does not require suturingTissue is removed in same manner as incisional/excisional

94Tissue Biopsy Interpretation: The biopsy report communicates the pathologist’s opinions concerning the specimen

to the practitioner The format includes:

Patient summaryGross description of the specimenMicroscopic description of the specimenThe diagnosisAdditional comments

95Tissue Biopsy Interpretation:Patient Summary:

It restates the patient information provided by the clinicianThe clinician should review this info to find out any inaccuracies that may affect

the diagnosisThe only new information is the Reference Number assigned to the specimen by

the pathologistAny future communications with the pathologist about the case must include this

reference number

96Tissue Biopsy Interpretation:Gross and Histopathologic descriptions

Gross description includes macroscopic features like colour , general shape and metric dimensions

Microscopic description includes the composition of the normal tissues and any abnormal findings

It can supplement the clinician’s understanding of the pathologist’s diagnosis and may reveal the severity of some lesions.

In addition, the microscopic description should indicate if the lesion extends to the specimen margins, which in cases of excisional biopsy may suggest the possibility of recurrence

97Tissue Biopsy Interpretation:Diagnosis:

This is the pathologist’s opinion of the patient’s condition based on the tissue specimen and the clinical information provided

The anatomic location of the lesion is usually specified after the diagnosis

Comments may be occasionally added by the pathologist to clarify an unusual or a non-specific diagnosis , suggest additional diagnostic procedures or recommend treatment methods

98Tissue Biopsy Interpretation:

99Exfoliative Cytology: Developed by Dr. George Papanicolaou who is also known as “Father of

cytology” In this, the surface of the lesion is either wiped with a sponge material or

scraped to make a smear. The appreciation of the fact that some cancer cells are so typical that they

can be recognized individually has allowed the development of this diagnostic technique

100Exfoliative Cytology:

Advantages:• Time saving• Painless• Low cost• No anaesthesia• Screening test• Rapid

diagnosis

Disadvantages:• Firm tumours• False negative

results• Non

assessment

Indications:• Patient

preference• Debilitated

patients• Adjunct• Rapid

evaluation• Population

screening

101Exfoliative Cytology:

Interpretation:

102Fine Needle Aspiration Cytology(FNAC):

Microscopic examination of an aspirate obtained by inserting a fine needle into a lesion

Painless and safe procedure for rapid diagnosis Indications:

Salivary gland pathologyAs a replacement for extensive biopsySuspicious lymph nodesRecurrenceMetastatic lesion

104Clinical Scenario 1:

Patient with generalized

periodontitis w/ multiple abscesses

Preliminary investigations:

CBC,FBS, PPBS, RBS

Occasionally:Glycated Hb/

OGTTRarely:ELISA


Patient presents with chronic fatigue, pallor

and paleness of conjunctiva

Preliminary investigations:CBC inc. Hb/Hct/Red cell indices

Absolute LC/DLC

Occasionally:Peripheral smear/ Serum Iron/ TIBC

Rarely:Schilling’s Test


Patient presents with recurrent bleeding

episodes/ persistent haemorrhage post

exodontia

Preliminary investigations:Platelet count/ BT/PT/aPTT

Occasionally:Bone Marrow

BiopsyRarely:

IHC

107Clinical Scenario 4 :

Patient diagnosed with a white lesion

Preliminary investigations:Toluidine blue/Lugol’s

Iodine/Vizilite/ CBC/Exfoliative Cytology

Definitive:Tissue biopsy

Rarely:IHC

108Clinical Scenario 5 :

Patient presents with burning sensation in

his mouth, provisional dignosis is RAS Major

Preliminary investigations:CBC(may exclude RAS)

Periodic CBC

Lesion persistent even after 6 weeks:Tissue biopsy

109Conclusion:

Lab investigations have become an integral component of a complete examination of the patient

They confirm the authenticity of our clinical impression and also provides a prognostic knowhow post treatment

As oral diagnosticians, we should have a thorough knowledge about different investigations pertaining to our field of study

We should also know how to correlate our history taking and clinical examination so as to order for the most appropriate investigation

110References:

1. Scully, Crispian ; Oral & Maxillofacial Medicine ; 2nd edition2. Prabhu, S.R. ; Textbook of Oral Medicine ; 1st edition3. Bricker, Langlais, Miller ; Oral Diagnosis, Oral Medicine and

Treatment Planning ; 2nd edition4. Mitchell, Standish, Fast ; Oral Diagnosis/Oral Medicine ; 3rd edition5. Coleman , Nelson ; Principle of Oral Diagnosis 6. www.google.com7. http://

www.nurseslearning.com/courses/nrp/labtest/course/section6/index.htm

http://www.google.com/

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laboratory investigations

Health & Medicine