A study was done to evaluate inter and intrareader differences in reading of smears stained by Fluorescent Method (FM) and Modified ZN Staining (CS) methods and variation in multiple smears made from the same specimens in order to find out to what extent sensitivity and specificity are influenced by repeated sputum smears from same specimens, by change of readers or by repeated reading.

Eighty sputum specimens with known results, 35 negative and 45 positive with different grades were selected. Ten smears were prepared from each specimen. All the smears were first examined by FM and later by CS method. Culture was also done for these specimens. The findings were: (i) FM was more sensitive than CS method. The specificity appeared to be equal in both. (ii) Change of readers influenced the relative sensitivity of both methods, but repeated examination by the same reader had no effect. (iii) Both reader as well as reading influenced the specificity of FM method but not that of CS method. (iv) Repeated sampling from the same specimen had no effect on the sensitivity of both the methods, while it had some effect on the specificity of FM method. (v) Consistency among readers and readings was found to be poor in smears with low grade positivity. (vi) The relative sensitivity of any method was influenced by the proportion of low grade positive cultures in the total pool. (vii) Examination of multiple smears from the same specimen by more than one reader and more than one reading by the same reader was more rewarding in CS method.