Abstract :
Introduction: Tuberculosis kills more people than any other communicable disease. Good diagnosis is
key to its prevention and control. While AFS is cost effective and widely used, CB-NAAT is costly and its
usage is increasing in recent times.
Objectives: to quantify the diagnostic capabilities of CB-NAAT and AFS in sputum samples suspected
pulmonary tuberculosis patients. To know the efficacy of AFS as a screening test against CB-NAAT as the
standard test.
Materials and Methods: Our cross sectional study analysed the results of 1210 sputum samples among
suspected pulmonary tuberculosis patients in whom both CB-NAAT and AFS was done during 2017-18.
Descriptive statistics with McNemar test (p predictive value for the tests have been used.
Results: Out of 1210 samples tested, AFS deteted positive in 13(1.07%) samples and CBNAAT was
positive in 173(14.29%) samples. There was statistically significant difference. Concordance in both the
tests positive in 13(1.07%) samples and negative in 1037(85.70%) sample was seen respectively. CBNAAT
as standard, sensitivity of AFS was 7.51%. Specificity was 100%. positive predictive value of AFS
was 100% and negative predictive value of AFS was 86.63%. AFS failed to detect 92.48% of the cases that
were diagnosed by CB-NAAT.
Conclusion: AFS was detected positive results in 1% of samples while CB-NAAT was positive results in
14% of samples. CB-NAAT was superior test compared to AFS. Concordance was 1% and 86% in positive
and negative results respectively. Sensitivity of AFS was very low while its specificity, positive predictive
value and negative predictive value was very superior.
Keyword :
CB-NAAT, Diagnostic capability, Sputum Microscopy, Sensitivity, Specificity.