Overdiagnosis of Tuberculosis and Role of Tuberculin Test

Abstract

This is a retrospective analysis of children who were referred to our tuberculosis (TB) clinic from March 2010 to Feb 2011 but were not started on ATT and none of them subsequently developed TB. Interpretation of tuberculin test as a means of diagnosis was analysed. Results: Thirty-four (11.2%) children were overly diagnosed as TB. Seventeen out of 28 referred children were tuberculin positive and 8 were tuberculin negative. Also, 12 of tuberculin positive children had a reading of ≥15mm, yet none of them developed active disease. Although 2 TU is the recommended standard dose for tuberculin testing in India, in our study no child had received 2 TU, 23.5% of tuberculin positive patients had received a 5 TU dose and 35.3% a 10 TU dose. Conclusion: Most children with over-diagnosis of TB receive TT with more than 2TU units. The size of tuberculin reaction needs to be interpreted carefully. Introduction A major challenge of childhood tuberculosis (TB) is establishing an accurate diagnosis. Less than 15% of cases are sputum acid-fast bacilli smear positive, and mycobacterial culture yields are 30%–40%.1 Diagnosis of most paediatric TB cases is dependent on the tetrad of 1) careful history (including history of TB contact and symptoms consistent with TB. 2) Clinical examination (including growth assessment). 3) Tuberculin Skin Testing with Tuberculin test (TT) 4) Lesions suggestive of active TB on chest radiography. However, in developing and endemic countries, most individuals acquire latent infection and become tuberculin positive in childhood itself and chest radiography can be difficult to assess. With difficulty of conclusive diagnosis, it can lead to overdiagnosis of TB. This retrospective study was undertaken to assess the overdiagnosis of TB, and to discuss the role of TT for treatment of TB, with emphasis on the prevalent practices of administration and interpretation of TT. Methods & Materials A retrospective study was carried out in the paediatric department of a tertiary care hospital in Mumbai. During the study period of March 2010 to Feb 2011, all patients who were diagnosed as TB and were referred from other centres to our TB clinic for starting Anti tuberculous therapy (ATT) were assessed. These children were diagnosed as TB based on either a positive tuberculin test; or symptoms suggestive of TB; or history of contact with a patient suffering from TB; or ultrasound (USG) abdomen showing abdominal lymph nodes; or palpable cervical lymph nodes. Children were assessed by detailed history, through physical examination and diagnostic investigations. In the historydetails on the presence of TB contact, previous TB infection, BCG vaccination status and symptoms of illness in the form of cough, fever, weight loss and loss of appetite were enquired. Investigation reports of child having undergone past tuberculin testing, the results of recent (within previous one month) tuberculin test done in other centres and findings of abdominal USG for lymph nodes was noted. Examination included general physical examination and assessment of nutritional status. Routine hemogram, and Chest X ray was done for all patients. In interpreting the tuberculin test, as per general practice, induration ≥10 mm was considered as positive with 5 TU unit. No patient had been investigated with cervical lymph node biopsy, TB Elisa, or QuantiFERON Gold Assay. Patients were not started on ATT if TT was positive with 10 TU units; if cervical nodes are less than 1cm and discrete; if abdominal nodes were non-matted, noncaseous; if the contact suffering from tuberculosis was not having open TB; patient had a recent positive TT with 5 TU units but also had a previous positive TT in the past; patient had recent TT with 5 TU units but had been treated with anti-tuberculous therapy in the past, and/or symptoms of the patient relieved in 2 weeks with other therapy. Data was analysed based on descriptive statistics. SPSS version 18 was used for statistical correlation of data with Fischer exact test. Address for Correspondance: Dr.Pradnya Paikrao Bansod, C/O K.N Dupare, PLOT No.6/7, Beside Nakshatra Heights, Near Balbharti, Rammohan Nagar, Amravati, Maharashtra 444607, India Email: paikraopl@gmail.com ©2021 Pediatric Oncall ARTICLE HISTORY Received 13 March 2021 Accepted 3 August 2021