Acid-fast Bacilli Smear Microscopy Research Articles

Metodologia para caracterização de proficiência em leitura de resultados baciloscópicos para o diagnóstico da tuberculose

To propose a methodology for characterizing proficiency in sputum smear microscopy for acid-fast bacilli (AFB) in the diagnosis of tuberculosis and to determine the number of microscopies necessary to establish this proficiency, as well as the quality of the transcription of results, the causes of the discrepancies in the readings (rater or microscope used), and the criterion for classification of microscopy results that poses the most difficulty in characterizing proficiency. Four hundred sputum smear microscopies for the diagnosis of tuberculosis were analyzed through double-blind readings by six professionals who usually read/supervise microscopies performed in public health care facilities. The sample was stratified to obtain, at least, a reliability of 90% in the double-blind readings, an alpha error of 5%, and a precision of 3%. The results were analyzed using observed reliability and the kappa index. Thirteen errors (0.27%) were found in the transcription of results. Reliability increased when the three distinct categories of positive results (AFB+, AFB++, and AFB+++) were grouped or when inconclusive results were excluded from the analysis. The quantification of the bacterial load was the classification criterion that posed the most difficulty in establishing proficiency. Using higher quality microscopes increased reliability. Reliability values stabilized only from the reading of 75 microscopies onward. Double-blind sputum smear microscopy readings using a panel containing 75 slides (36 negative, 4 inconclusive, and 35 positive) proved to be appropriate for characterizing proficiency in sputum smear microscopy for the diagnosis of tuberculosis when such proficiency is intended to reproduce laboratory routine.

Comparison With The Smart Check Recombinant TB Serology Assay And Direct Sputum Microscopy For Acid Fast Bacilli Among Suspected HIV Positive Patients In Northeastern Nigeria

Currently, the Sputum smear microscopy for acid fast bacilli is the corner stone of diagnosis of HIV associated active TB in Nguru, Northeastern Nigeria. This method has low sensitivity and specificity. In this study, we set out to compare the reliability of the Smart Check Recombinant TB rapid test kit with the routine direct sputum microscopy for acid- fast bacilli (AFB). Using Ziehl-Neelsen stained sputum smear microscopy for AFB as the standard, sensitivity and specificity of the Smart Check Recombinant TB rapid test kit was 96.7 % and 82.1 % respectively. These results show that the performance of the Smart Check Recombinant TB rapid test kit was adequate in comparison with direct sputum smear microscopy by sensitivity and specificity for the diagnosis of active TB in HIV infected patients when alternative is just clinical suspicion.

Quality assessment of sputum smears microscopy for detection of acid fast bacilli in peripheral health care facilities in Dar es Salaam, Tanzania

There is no published information regarding the quality of sputum smear microscopy in Tanzania. To evaluate technical quality and results of smear microscopy for acid-fast bacilli (AFB) in peripheral health care facilities in Kinondoni and Ilala Districts in Dar es Salaam, Tanzania. Cross-sectional study. All tuberculosis diagnostic centres in Dar es Salaam, Tanzania. The proportion of well prepared smears was 86.2% and that of well stained smears was 81.2%. The overall average agreement in reading was (89.2%). The overall sensitivity was 88.5% and specificity was 100%. High false negatives (HFN) were the major errors found in this study and Low false negative (LFN) and quantification errors (QE) were the minor errors found. There were no false positive errors. Minor errors occurred more frequently in hospitals than dispensaries, while major errors occurred more frequently in dispensaries than in hospitals. The types of errors found in this survey, HFN, LFN and QE, suggest a systematic under-reading of smears in all the surveyed health facilities, probably due to a number of technical factors (quality of smears, poor stains, bad microscopes, or inadequate training) and other factors such as overwork and lack of motivation which need to be addressed. Regular supervision using the new WHO quality assurance guidelines should be conducted countrywide. We do recommend that blind re-checking as the most efficient means of making the first broad assessment of sputum smear microscopy in Tanzania.

Impact of short-course therapy on tuberculosis drug resistance in South-West Burkina Faso

Setting: The Regional Tuberculosis Centre and the Muraz Centre in Bobo-Dioulasso, Burkina Faso. Objectives: To observe the trend of primary drug resistance in pulmonary tuberculosis patients 5 years into a short-course treatment programme and to assess the possible implementation of a further programme. Design: Bacteriological study of stains isolated from all newly diagnosed tuberculosis patients ( n = 300), all relapse cases ( n = 20) and all failure cases ( n = 58) from the Houet province, during the period from April 1992 to April 1994. Human immunodeficiency virus (HIV) serostatus was determined for the first 119 patients included in the study. Results:Mycobacterium tuberculosis was the predominant species as shown by 75.1% of the isolates; next was M. africanum, then atypical mycobacteria and finally M. bovis, representing 18.4%, 6.5% and 0.4% of the isolates respectively. Primary resistance (excluding atypical strains) was as follows: isoniazid 7.6%, ethambutol 1.0%, rifampicin 2.5%, and streptomycin 12.4%; 33.6% of the patients tested for HIV were HIV positive. There was no relationship between HIV serostatus and the identity of strains or drug resistance. However, negative acid-fast bacilli smear microscopy with positive culture was significantly more frequent in HIV-positive patients than in HIV-negative patients. Conclusion: This study shows a drop in primary resistance compared with previous studies carried out in Bobo-Dioulasso under the same conditions (setting, materials and methods, sampling procedures) in 1982 and 1986. This is consistent with the hypothesis that treatment monitoring and the introduction of short-course therapy in 1989 (2 HERZ/4 HR or 2 HRSZ/4 HR) have contributed to lower rates of primary drug resistance.