PURPOSE:

This calculator is meant to help programs decide on screening and diagnostic algorithms for TB active case-finding.  It estimates the bacteriologic testing resources required and the number of bacteriologically confirmed cases that would be expected based on different screening and testing methods.  Performing clinical and radiographic examinations for all people who screen positive would enable clinical diagnoses and would increase the number of cases detected; however, these procedures are not considered by this calculator.

The default values for the performance of different screening and bacteriologic testing methods have been taken from studies on adults with culture-confirmed pulmonary TB (including both HIV-positive and HIV-negative adults). These methods generally have poorer performance in children and people with extra-pulmonary TB.  If an active case-finding program is being planned for a population comprising many children or a very large proportion of PLHIV, custom sensitivity and specificity numbers should be entered.



REFERENCES:

Sensitivity and specificity estimates for screening methods reflect meta-analysis pooled estimates from the World Health Organization 2013 document "Systematic screening for active tuberculosis: an operational guide" avaialble at https://www.who.int/tb/publications/systematic_screening/en/

Sensitivity estimate for Xpert reflects meta-analysis pooled estimate compared to a reference standard of culture-confirmed pulmonary TB in adults. Reference: Horne DJ et al. Xpert MTB/RIF and Xpert MTB/RIF Ultra for pulmonary tuberculosis and rifampicin resistance in adults. Cochrane Database Syst Rev 2019; 2019(6):CD009593.

Sensitivity estimate for smear microscopy reflect meta-analysis pooled estimate of conventional examination of two smears with Ziehl-Neelsen light microscopy over 2 days, compared to a reference starndard of culture-confirmed pulmonary TB in adults.  Reference: Davis LJ et al. Diagnostic accuracy of same-day microscopy versus standard microscopy for pulmonary tuberculosis: a systematic review and meta-analysis. Lancet Infectious Diseases 2013; 13(2):147-54.