SPECIMEN COLLECTION METHODS IN THE DIAGNOSIS OF CHILDHOOD.pptx

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1. SPECIMEN COLLECTION METHODS IN THE DIAGNOSIS OF CHILDHOOD TUBERCULOSIS PUBLISHED IN - INDIAN JOURNAL OF MEDICAL MICROBIOLOGY MODERATOR - DR. MAYURI BARUAH PRESENTOR - DR. ANANYA TIWARI

2. INTRODUCTION Of the estimated 8.3 million new TB cases reported to World Health Organisation (WHO) in 2000, 884019 (11%) were children. Diagnosis of childhood TB is complicated. Sputum Microscopy, often the only test available in endemic areas, is positive in less than 10-15% of children with probable TB and culture yields are usually low (30-40%) For this reason, in non-endemic areas, use of diagnostic triad is widely advocated: 1) Known contact with an adult index case ( eg : household contact) 2) A positive Tuberculin Skin Test (TST) as evidence of M. tuberculosis infection 3) Suggestive signs on chest radiograph (CXR)

3. SAMPLE COLLECTION SPUTUM : Not feasible in very young children. Assistance and supervision may improve the quality of the specimen. Routine sample to be collected in children >7 yrs of age ( all children who can produce good quality specimen)

4. b) Induced sputum : Non Invasive approach. Increased yield compared to gastric aspirate. No age restriction. Specialized technique, which requires nebulization and suction facilities. To be considered in the hospital setting, use outside hospital setting not studied. A South African study showed that a single specimen, using hypertonic saline induced sputum collection, may provide same yield as 3 gastric aspirate specimen. Potential transmission risk.

5. c) Gastric aspirate: Difficult and Invasive procedure. Not easily performed on an out patient basis. Requires prolonged fasting. Sample collection advised on 3 consecutive days. Routine sample to be collected in the hospitalized who cannot produce a good quality sputum specimen. A retrospective study from California compared the bacteriologic yield achieved in gastric aspirates collected from hospitalized and non- hospitalized children. Although the yield in hospitalized children was higher (percentage of positive cultures 48% vs 37%), this suggests that hospitalization may not be a prerequisite for the collection of good gastric aspirate specimen.

6. D) STRING TEST: Less invasive than gastric aspirate. Tolerated well in children >4 yrs. Potential to become a routine sample collected in children who can swallow the capsule but cannot produce a good quality sputum specimen. It consists of a coiled nylon string inside a gel capsule. The string unravels through a hole in the end of the weighted capsule as it descends into the stomach and the capsule then dissolves in the stomach. The unraveled string becomes coated with gastro-intestinal secretions and pathogens, if present, are retrieved when the string is extracted 4 hours later.

7. E) BRONCHO-ALVEOLAR LAVAGE: Extremely invasive Only for use in patients who are intubated or who require diagnostic bronchoscopy. Broncho-alveolar lavage, using flexible fiberoptic bronchoscopy, has additive value when used in combination with gastric lavage. In a study from Peru, mid morning nasopharyngeal aspiration was compared with early morning gastric aspiration; gastric aspiration provided a slightly better yield (38% vs 30%), but results were comparable. F) NASOPARYNGEAL ASPIRATION: Less invasive than gastric aspirate. No fasting or hospitalization required. Can be performed at any time of the day. Comparable yield to gastric aspirate. To be considered in primary health care clinics or on an out-patient basis.

8. G) URINE/STOOL: Not invasive. To be considered with novel sensitive bacteriologic or antigen based tests. H) BLOOD/BONE MARROW: To be considered for confirmation of probable disseminated TB in hospitalized patients. Blood draw may be indicated for performing serological assay for TB and for diagnosis of latent infection using interferon-gamma release assays (IGRAs). IGRAs are more specific than the TST for detection of latent TB infection, they have limited applicability due to- a) highly expensive b) require laboratory infrastructure

9. SPECIMEN PROBLEMS/BENEFIT POTENTIAL CLINICAL APPLICATION SPUTUM Not feasible in very young children. Assistance and supervision required. Routine sample to be collected in children >7yrs of age. INDUCED SPUTUM Increased yield compared to gastric aspirate. No age restriction. Requires nebulization and suction facilities. Use outside hospital setting not studied. Potential transmission risk. To be considered in the hospital setting on an in- or out- patient basis. SUMMARY

10. CONT… SPECIMEN PROBLEMS/BENEFITS POTENTIAL CLINICAL APPLICATION GASTRIC ASPIRATE Difficult and invasive Requires prolonged fasting Sample collection to be done on 3 consecutive days. Routine sample to be collected in the hospitalized who cannot produce a good quality sputum specimen. STRING TEST Less invasive. Tolerated well in chidren >4yrs. Potential to become routine sample in children who can swallow the capsule but not produce good quality sputum. NASOPHARYNGEAL ASPIRATION Less invasive No fasting required Comparable yield to gastric aspirate. To be considered in PHC or on an out patient basis.

11. CONT… SPECIMEN PROBLEMS/BENEFITS POTENTIAL CLINICAL APPLICATION BRONCHO-ALVEOLAR LAVAGE Extremely invasive Only for use in patients who are intubated or who require diagnostic bronchoscopy. URINE/STOOL Not invasive Excretion of M. tuberculosis well documented To be considered with novel sensitive bacteriologic or antigen-based tests. BLOOD/BONE MARROW Good sample sources to consider in the case of probable disseminated TB. To be considered for the confirmation of probable disseminated TB in hospitalized patients.