Acid fast bacilli (AFB) microscopy: The place of cold staining method in tuberculosis diagnosis in Jos, Plateau State, Nigeria. – U.E. Emanghe, G.I. Ogban, M.O. Okolo, E.B. Banwat and D.Z. Egah
ABSTRACT
An evaluation of known staining methods like the kinyoun (cold method) is imperative for wide accessibility of tuberculosis diagnosis to further enhance the success of DOTS (Directly Observed Therapy Short) course which is the main strategy of TB management and control. The ZN (Ziehl-Neelsen) and Kinyoun staining methods were compared based on their ease of performance and relative sensitivity, specificity, positive and negative predictive values against the background of culture positivity on LJ (Loweinstein-Jensen) media at the Jos University Teaching Hospital (JUTH), Jos, Plateau State, Nigeria. Out of the 72 patients enlisted in this study, 15 were culture positive for M. tuberculosis. The technique detected 13 (18.1%) as smear positive for AFB and the cold method 12 (16.7%). Of the 15 culture positive cases, ZN and cold method detected 7 and 6 cases, respectively as AFB positive giving sensitivity values of 86.7% and 80.0% for ZN and cold technique, respectively. The work also recorded specificities of 89.5% and 91.2%, respectively for ZN and cold staining methods. The positive predictive and negative predictive values were 53.8% and 86.4%, respectively for ZN technique and 58.3% and 80.6%, respectively for cold method. This work did not demonstrate any significant difference in the abilities of culture on L-J media and ZN and cold staining methods to detect tubercle bacilli in the diagnosis of TB. It is therefore reasonable to conclude that these staining methods can be depended upon for routine diagnosis in resource-poor countries like Nigeria. In addition, the cold method is user-friendly, simpler with comparable result as the traditional ZN method.