Comparative evaluation of Ziehl- Neelsen staining and kinyoun’s staining in the diagnosis of clinically suspected cases of tuberculosis

Abstract

: Tuberculosis commonly affects lungs but can also be ex­tra-pulmonary. The increasing prevalence of extra-pulmonary manifestation of tuberculosis is a cause for concern. Microbiological diagnosis is essence for the effective treatment of mycobacterium tuberculosis. The smear detection tests differentiate infectious from non-infectious cases. Both Ziehl-Neelsen (Z-N) and kinyoun stain (KC) methods are over 100 years old; these are most economical in terms of processing time, needed equipment and personnel. The objective of research was to evaluate the two smear microscopy methods for the detection of tubercle bacilli in the sputum and Fine needle aspiration cytology (FNAC) material by comparing the sensitivity, specificity and validities of kinyoun’s method against Z-N staining.A prospective and comparative study was carried using 500 sputum samples and 100 FNAC material received in the department. All the 600 samples were subjected to two methods:Z-N stain and Kinyoun’s cold stain. They were compared for sensitivity and specificity in terms of qualitative results and grades of smear as recommended by RNTCP. : The smear positivity rate was 18% and 20.16% in Ziehl-Neelsen stain and Kinyoun’s cold stain respectively. The direct smear microscopy for Z-N staining showed sensitivity, 89.25%, specificity and positive predictive value (PPV) 100% and negative predictive value (NPV) 97.35% whereas KC method showed sensitivity 98.37%, specificity and PPV 100% and NPV 99.58% respectively. Kinyon’s method described is slightly longer to perform than the Ziehl-Neelsen technique but its ease of use and equal efficacy with Z-N method make it universally applicable, especially in those laboratories where facilities are poor.