Abstract
Background: The reliability of direct smear microscopy for diagnosis of tuberculosis (TB) using Ziehl-Neelsen (ZN) technique has frequently been questioned due to low sensitivity. Fluorescent microscopy (FM) is more sensitive than ZN but its sensitivity is less than culture. Treatment of sputum with bleach has been used to increase sensitivity in many settings. However, no study has compared use FM and ZN methods for detection of acid-fast bacilli (AFB) using bleach method. Objectives: Comparison of results with fluorescence and bright-field microscopy for AFB using bleach centrifugation method. Methods: Three hundred and seventy sputum specimens were collected from new TB suspects attending Mbagathi District Hospital and processed for direct microscopy using both ZN and FM. Culture on Loweinstein Jensen egg media was used as the gold standard. FM and ZN smear negative specimens were treated with 3.5% bleach and left to stand for 30 minutes before centrifugation. Smears were prepared from each bleach treated specimen, processed and examined using either ZN or FM staining methods. Results: Of the 370 specimens, 200(54%) were culture positive. The number of smear positive by direct ZN was 138 (37.2%) which increased to 171 (46.2%) and direct FM positive was 165 (44.6%) which increased to 180 (48.6%), after treatment of direct ZN and FM smear negative specimens with 3.5% bleach, respectively. There was a significant increase in sensitivity from 66% to 81.1% (p < 0.05) using ZN technique and 75.5% to 83% (p < 0.05). Conclusion: Bleach centrifugation method significantly increases the sensitivity of smear negative specimens irrespective of the staining method used. However, FM appears to be more sensitive than ZN. 13th International Congress on Infectious Diseases Abstracts (Oral Presentations)International Journal of Infectious DiseasesVol. 12Preview Full-Text PDF Open Archive
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