Abstract
Background and Objectives. Low counts are more difficult to find in microscopic sputum examination and thus are more likely to be missed. In this study, we aimed to estimate the proportion of low-count grading and assessing any age and gender differences in sputum smear grading in a low HIV prevalence setting. Materials and Methods. From the tuberculosis laboratory register information on sputum positivity including the grading of smears, age and gender were extracted for January 2011–December 2011. Smears were examined using Ziehl-Neelsen technique and graded as per the Program Guidelines. Positive smears were classified into low grade positive smears (scanty and 1+) and high grade positive smears (2+ and 3+). Differences in grading of smear based on gender and age were analysed using chi square test. Results. Of 9000 smears examined, 8210 (91.2%) were collected as diagnostic smears from tuberculosis suspects. Low grade positivity was 37.5% among diagnostic smears and 69.6% among follow-up smears. Sputum smears from female examinees had higher proportions of low grade positive smears (P=0.003). Stratification of age and sex within TB suspects had clearly demonstrated the observance of higher low grade positivity among female TB suspects at extremes of age.
Highlights
Sputum smear microscopy remains the mainstay in the diagnosis of pulmonary tuberculosis in many developing countries including India
Though newer techniques like real time cartridge based nucleic acid amplification test (CBNAAT) with higher sensitivity and specificity have been introduced in fewer centres in India; good quality sputum microscopy remains the backbone in the diagnosis of pulmonary tuberculosis under Revised National Tuberculosis Control Program (RNTCP)
Sensitivity of the sputum smear microscopy depends on many factors like quality of sputum obtained from patients, concentration of bacilli in the sputum, skill of the laboratory personnel in staining procedure, and duration between sputum sample collection and smear examination [1]
Summary
Low counts are more difficult to find in microscopic sputum examination compared to higher counts (grade) and are more likely to be missed [7]. The frequency of low-count grading results compared with high count grading has been considered as an indicator of the quality of sputum smear microscopy [8]. Age and gender differences in grading of smears were reported in high HIV prevalence settings [9]. We aim to estimate the relative frequency of low-count grading and assessing any age and gender differences in sputum smear grading in a low HIV prevalence setting. We aimed to estimate the proportion of low-count grading and assessing any age and gender differences in sputum smear grading in a low HIV prevalence setting. Stratification of age and sex within TB suspects had clearly demonstrated the observance of higher low grade positivity among female TB suspects at extremes of age
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