Cargando…

Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa

BACKGROUND: Optimum sputum results for acid-fast bacilli (AFB) microscopy are linked to a sputum quantity of at least 5.0 mL. This study was aimed at establishing the effect of sputum quantity in the pick-up rate of AFB microscopy by comparing sputum samples of 5.0 mL and 2.0 mL. METHODS: An analyti...

Descripción completa

Detalles Bibliográficos
Autores principales: Rashid, Iqbal, Mabuza, Langalibalele H., Govender, Indiran, Pretorius, Deidre
Formato: Online Artículo Texto
Lenguaje:English
Publicado: AOSIS OpenJournals 2011
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4565445/
http://dx.doi.org/10.4102/phcfm.v3i1.240
_version_ 1782389575948173312
author Rashid, Iqbal
Mabuza, Langalibalele H.
Govender, Indiran
Pretorius, Deidre
author_facet Rashid, Iqbal
Mabuza, Langalibalele H.
Govender, Indiran
Pretorius, Deidre
author_sort Rashid, Iqbal
collection PubMed
description BACKGROUND: Optimum sputum results for acid-fast bacilli (AFB) microscopy are linked to a sputum quantity of at least 5.0 mL. This study was aimed at establishing the effect of sputum quantity in the pick-up rate of AFB microscopy by comparing sputum samples of 5.0 mL and 2.0 mL. METHODS: An analytical cross-sectional study was carried out at the Dr George Mukhari Hospital (DGMH) in Pretoria, South Africa, from 05 January 2007 to 04 January 2008. Two sputum samples, 5.0 mL and 2.0 mL, were collected from each of the 330 adult PTB (pulmonary tuberculosis) suspects. Fluorescence microscopy was used in the sputum analysis. The yield through microscopy of the 2.0 mL specimen versus the 5.0 mL specimen was compared and analysed, using culture results as the gold standard. RESULTS: From a sample of 330 specimens, 77 tested AFB positive on microscopy. In the 5.0 mL samples, the sensitivity was 76.6% (95% CI, 66.0% – 84.7%), specificity 99.6% (95% CI 97.8% – 99.9%), positive predictive value (PV+) 98.3% (95% CI 91.1% – 99.7%), negative predictive value (PV-) 93.3% (95% CI 89.7% – 95.7%), the likelihood ratio (LR) for a positive microscopy 192 and the LR for a negative test was 0.23. In the 2.0 mL specimens, the sensitivity was 75.3% (95% CI 64.6% – 83.6%), specificity 99.2% (95% CI 97.1% – 99.8%), positive predictive value (PV+) 96.7% (95% CI 88.6% – 99.1%), negative predictive value (PV-) 93.0% (95% CI 89.3% – 95.4%), the LR for a positive microscopy was 94 and 0.25 for a negative microscopy. There was a statistically significant association (p-value < 0.001) between the microscopy and culture tests in both the 5.0 mL and the 2.0 mL specimen categories. The strength of association between the microscopy and culture, as indicated by the kappa test was 0.83 and 0.81 in the 5.0 mL and 2.0 mL categories, respectively. CONCLUSION: Compared to the 2.0 mL specimen category, the yield for AFB microscopy in the 5.0 mL specimen category was consistently superior, as indicated by the higher sensitivity, specificity, predictive values and the likelihood ratios in the 5.0 mL specimen category. It is recommended that sputum specimen collection for AFB microscopy should aim for a minimum volume of 5.0 mL.
format Online
Article
Text
id pubmed-4565445
institution National Center for Biotechnology Information
language English
publishDate 2011
publisher AOSIS OpenJournals
record_format MEDLINE/PubMed
spelling pubmed-45654452016-02-03 Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa Rashid, Iqbal Mabuza, Langalibalele H. Govender, Indiran Pretorius, Deidre Afr J Prim Health Care Fam Med Original Research BACKGROUND: Optimum sputum results for acid-fast bacilli (AFB) microscopy are linked to a sputum quantity of at least 5.0 mL. This study was aimed at establishing the effect of sputum quantity in the pick-up rate of AFB microscopy by comparing sputum samples of 5.0 mL and 2.0 mL. METHODS: An analytical cross-sectional study was carried out at the Dr George Mukhari Hospital (DGMH) in Pretoria, South Africa, from 05 January 2007 to 04 January 2008. Two sputum samples, 5.0 mL and 2.0 mL, were collected from each of the 330 adult PTB (pulmonary tuberculosis) suspects. Fluorescence microscopy was used in the sputum analysis. The yield through microscopy of the 2.0 mL specimen versus the 5.0 mL specimen was compared and analysed, using culture results as the gold standard. RESULTS: From a sample of 330 specimens, 77 tested AFB positive on microscopy. In the 5.0 mL samples, the sensitivity was 76.6% (95% CI, 66.0% – 84.7%), specificity 99.6% (95% CI 97.8% – 99.9%), positive predictive value (PV+) 98.3% (95% CI 91.1% – 99.7%), negative predictive value (PV-) 93.3% (95% CI 89.7% – 95.7%), the likelihood ratio (LR) for a positive microscopy 192 and the LR for a negative test was 0.23. In the 2.0 mL specimens, the sensitivity was 75.3% (95% CI 64.6% – 83.6%), specificity 99.2% (95% CI 97.1% – 99.8%), positive predictive value (PV+) 96.7% (95% CI 88.6% – 99.1%), negative predictive value (PV-) 93.0% (95% CI 89.3% – 95.4%), the LR for a positive microscopy was 94 and 0.25 for a negative microscopy. There was a statistically significant association (p-value < 0.001) between the microscopy and culture tests in both the 5.0 mL and the 2.0 mL specimen categories. The strength of association between the microscopy and culture, as indicated by the kappa test was 0.83 and 0.81 in the 5.0 mL and 2.0 mL categories, respectively. CONCLUSION: Compared to the 2.0 mL specimen category, the yield for AFB microscopy in the 5.0 mL specimen category was consistently superior, as indicated by the higher sensitivity, specificity, predictive values and the likelihood ratios in the 5.0 mL specimen category. It is recommended that sputum specimen collection for AFB microscopy should aim for a minimum volume of 5.0 mL. AOSIS OpenJournals 2011-10-14 /pmc/articles/PMC4565445/ http://dx.doi.org/10.4102/phcfm.v3i1.240 Text en © 2011. The Authors http://creativecommons.org/licenses/by/2.0/ AOSIS OpenJournals. This work is licensed under the Creative Commons Attribution License.
spellingShingle Original Research
Rashid, Iqbal
Mabuza, Langalibalele H.
Govender, Indiran
Pretorius, Deidre
Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa
title Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa
title_full Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa
title_fullStr Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa
title_full_unstemmed Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa
title_short Volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the Dr George Mukhari Hospital, South Africa
title_sort volume of sputum to detect acid-fast bacilli as a measure of quality for the diagnosis of pulmonary tuberculosis at the dr george mukhari hospital, south africa
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4565445/
http://dx.doi.org/10.4102/phcfm.v3i1.240
work_keys_str_mv AT rashidiqbal volumeofsputumtodetectacidfastbacilliasameasureofqualityforthediagnosisofpulmonarytuberculosisatthedrgeorgemukharihospitalsouthafrica
AT mabuzalangalibaleleh volumeofsputumtodetectacidfastbacilliasameasureofqualityforthediagnosisofpulmonarytuberculosisatthedrgeorgemukharihospitalsouthafrica
AT govenderindiran volumeofsputumtodetectacidfastbacilliasameasureofqualityforthediagnosisofpulmonarytuberculosisatthedrgeorgemukharihospitalsouthafrica
AT pretoriusdeidre volumeofsputumtodetectacidfastbacilliasameasureofqualityforthediagnosisofpulmonarytuberculosisatthedrgeorgemukharihospitalsouthafrica