Comparison between specificity and sensitivity of sodium hydroxide and sodium hypochlorite concentration methods for the diagnosis of AFB
Keyword : AFB, Sodium hydroxide, Sodium hypochlorite, Sensitivity, Specificity.
Author(s) : Chukwujekwu, Chinedu Reuben And Elomba, C. Chidozie
Abstract : Identification of Mycobacterium in the clinical laboratory by microscopy is important for initial diagnosis of Acid Fast Bacilli (AFB) but with low sensitivity and specificity. This work compared specificity and sensitivity of sodium hydroxide (NaOH) concentration method (Control) versus sodium hypochlorite (NaOCl) concentration method (Test) for AFB diagnosis, so that the more specific and sensitive method will improve diagnosis of AFB. Three hundred and five (305) clinical samples of sputum, laryngeal swab, gastric and cerebrospinal fluid from suspected tuberculosis patients were analyzed in Jos University Teaching Hospital. In both control and test methods, specimens were concentrated and deposit smear made on a clean slide and stained with AFB staining technique. A total of 54 samples (17.7%) were positive for AFB with NaOH method while 38 samples (12.5%) were positive with NaOCl method. The NaOH method diagnosed 16 additional patients, which constituted a rise of 5.2%. Moreover, NaOH and NaOCl specificity in detecting AFB were 87.54% and 82.29% respectively while their sensitivity were 100% and 70.37%. This indicated that NaOH concentration method has advantage over NaOCl concentration method even when both are simple, safe, not requiring additional training or expensive reagents.