Bonnet, M., Ramsay, Andrew, Gagnidze, L., Githui, W., Guerin, R. J. and Varaine, F. (2007) 'Reducing the number of sputum samples examined and thresholds for positivity: an opportunity to optimise smear microscopy'. International Journal of Tuberculosis and Lung Disease, Vol 11, Issue 9, pp. 953-958.
Full text not available from this repository. (Request a copy)Abstract
SETTING: Urban health clinic, Nairobi.
OBJECTIVE: To evaluate the impact on tuberculosis (TB) case detection and laboratory workload of reducing the number of sputum smears examined and thresholds for diagnosing positive smears and positive cases.
DESIGN: In this prospective study, three Ziehl-Neelsen stained sputum smears from consecutive pulmonary TB suspects were examined blind. The standard approach (A), >= 2 positive smears out of 3, using a cut-off of 10 acid-fast bacilli (AFB)/100 high-power fields (HPF), was compared with approaches B, >= 2 positive smears (>= 4 AFB/100 HPF) out of 3, one of which is >= 10 AFB/100 HPF; C, >= 2 positive smears (>= 4 AFB/100 HPF) out of 3; D, >= I positive smear (>= 10 AFB/100 HPF) out of 2; and E, >= I positive smear (>= 4 AFB/100 HPF) out of 2. The SUMMARY microscopy gold standard was detection of at least one positive smear (>= 4 AFB/100 HPF) out of 3.
RESULTS: Among 644 TB suspects, the alternative approaches detected from 114 (17.7%) (approach B) to 123 cases (19.1%) (approach E) compared to 105 cases (16.3%) for approach A (P < 0.005). Sensitivity ranged between 82.0% (105/128) for A and 96.1% (123/128) for E. The single positive smear approaches reduced the number of smears by 36% compared to approach A.
CONCLUSION: Reducing the number of specimens and the positivity threshold to define a positive case increased the sensitivity of microscopy and reduced laboratory workload.
Item Type: | Article |
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Uncontrolled Keywords: | tuberculosis microscopy diagnosis scanty afb smears pulmonary tuberculosis diagnosis prevalence efficiency culture |
Subjects: | WF Respiratory System > Tuberculosis > WF 220 Diagnosis. Prognosis |
Faculty: Department: | Groups (2002 - 2012) > Clinical Group |
Depositing User: | Ms Julia Martin |
Date Deposited: | 03 Sep 2010 10:45 |
Last Modified: | 06 Feb 2018 13:01 |
URI: | https://archive.lstmed.ac.uk/id/eprint/1344 |
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