Effectiveness of Concentration Technique in Smear Microscopy for M. Tuberculosis Diagnosis

Background: Revised National Tuberculosis Control Program (RNTCP) started as pilots in October 1993 and in 1997 it was launched as a national programme. By March 2006, entire country has been covered under the programme. But still the figures are high. In RNTCP, microscopic examination of sputum for Acid Fast Bacilli (AFB) plays an important role in the initial diagnosis of tuberculosis. Bacillary concentration after decontamination and liquefaction by 4% sodium hydroxide (Petroff's method) is useful in providing increased sensitivity and safety for handling of specimen. Materials and Methods: In this cross-sectional, prospective study, carried out at MLB Medical College and Hospital, Jhansi, patients were included according to RNTCP criteria. One set of smears was made according to the RNTCP guidelines while another set was prepared by concentration after decontamination with 4% sodium hydroxide (Petroff's method). Both set of smears were stained according to RNTCP method and were screened and graded according to the RNTCP guidelines. A total of 1152 sputum samples from 384 patients were included in the study with 254 males (66.14%) and 130 females (33.85%). Results: A total of 578 samples (50.17%) from 198 patients were positive by routine method whereas by concentration method 653 samples (56.68%) from 223 patients were found positive diagnosing 25 additional patients. This rise of 6.51% in sputum positivity over routine is highly significant (P=0.002, χ2=9.81) with 12.62% increase in diagnosed cases. Conclusion: There is a statistically significant rise in smear positive cases after concentration with 4% sodium hydroxide solution (Petroff's method). Considering its increased sensitivity of sputum microscopy, low cost, decontaminating and liquefaction properties, this method is safe and can be of vital importance, at least for smear negative cases.