Sensitivity and specificity of screening tools and smear microscopy in active tuberculosis case finding

SETTING

Community based five pulmonary tuberculosis (PTB) surveys among adults.

OBJECTIVES

Estimate sensitivity and specificity of screening tools for PTB and sputum microscopy.

METHODS

For each survey site, we estimated sensitivity and specificity of different screening criteria and microscopy against culture; pooled estimates were obtained using Random Effects Model.

RESULTS

Sensitivity of cough alone, screening for any symptom (persistent cough ≥2 weeks, fever or chest pain ≥1 month, hemoptysis), any symptom or history of anti-TB treatment (h/o ATT) were 56.2%, 66% and 71.2% respectively; specificities were 95.3%, 93.8% and 92.7% respectively. X-ray when used alone for primary screening had sensitivity and specificity of 76.6% and 97.3% respectively. When used along with screening for cough, these figures were 94.3% and 93.1%, and 100% and 97.3% when used with any symptom and h/o ATT. When used for secondary screening, sensitivity and specificity of X-ray was 66.8% and 87.8% respectively after primary screening for cough, 65.0% and 89.8% after screening for any symptom, and 67.1% and 86.7% when used after screening for any symptom or h/o ATT. Pooled sensitivity and specificity of smear was 46.2% and 99.3% respectively.

CONCLUSION

Program managers may use these estimates while evaluating algorithms for active case finding.

Prevalence of pulmonary tuberculosis in Wardha district of Maharashtra, Central India

A house based survey was conducted during 2007–2009 in a representative sample of population in Wardha district implementing Directly Observed Treatment Short Course strategy for tuberculosis (TB) control since 2001. The objective was to estimate prevalence of bacillary pulmonary TB (PTB) in individuals aged 15 years or above, and to estimate trends in prevalence when compared to a previous survey carried out in mid 1980’s. Two sputum samples (one spot, one early morning) collected from individuals having symptoms suggestive of PTB, history of previous anti-TB treatment (ATT) or abnormal pulmonary shadow on Mass Miniature Radiography (MMR) consistent with possibly or probably active tuberculosis were subjected to Ziehl–Neelsen microscopy and culture on Lowenstein–Jensen medium.

Of 55,096 individuals registered into the survey, 50,332 (91.4%) were screened by interview for symptoms and history of ATT and/or by MMR. Of them, 4805 were eligible for sputum collection; both specimens were collected in 4285 (89.2%) and only one specimen in 27 (0.6%).

A total of 86 bacillary cases were detected during the survey. Prevalence of bacillary PTB was estimated at 188.7 (140.3–236.9) per 100,000 populations. There was a decline of 61% in the prevalence of PTB over a period of 22 years.