| Summary: | Background: Tuberculosis remains a major public health problem worldwide. Direct Ziehl Nelseen (ZN) is the conventional Laboratory method for diagnosis of TB. However, there are higher chances of missing TB positive cases due to insufficient sensitivity. This would eventually lead to TB transmission and hence mortality.
Objective: To determine sensitivity and specificity of ZN diagnostic technique on concentrated and unconcentrated sputum samples as well as to assess how clinical, socio-demographic, and sample variables affect concentrated sputum ZN positivity.
Method and Materials: This cross-sectional investigation was carried out in Mulago Hospital, covering adult TB presumptive patients. Sputum samples from 114 patients were collected and processed by both NaOCl concentration and direct ZN diagnostic techniques. Sensitivity and specificity were calculated and tabulated. Prediction of ZN positivity was assessed using Logistic regression analysis.
Results: Out of the total 114 samples, 82 (71.9%) were positive by GeneXpert test (the gold standard), whereas by NaOCl concentration method 79 samples (69.3%) were found positive but with direct ZN method 65 samples (57.0%) were found positive, thus an increase of 14 samples (12.3%) in positivity was noted when used NaOCl concentration method which is highly significant with ρ<0.05 (χ2 =95.38). NaOCl concentration method got a higher sensitivity than direct sputum smear with 97.5% and 80.2% respectively. The specificities were almost the same with NaOCl method 93.9% and direct sputum smear with 90.9%. NaOCl concentration method had a PPV of 0.98 and NPV of 0.94 while direct sputum smear had PPV of 0.95 and NPV of 0.65.
Conclusion: NaOCl concentration method was found to be more sensitive than direct ZN though the specificity was almost the same. Clinical, socio-demographic and sample factors’ effect on ZN positivity was not statistically significant (ρ value=0.796). NaOCl concentration method should be adopted for effective diagnosis of pulmonary TB.
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