External Quality Assessment of AFB Smear Microscopy in Tuberculosis

Asfaw, Fanaye (2009) External Quality Assessment of AFB Smear Microscopy in Tuberculosis. Masters thesis, Addis Ababa University.

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Abstract

Tuberculosis is the world's most serious infectious disease, with over 2 million deaths each year. About a third of the world’s populations are latently infected with Mycobacterium tuberculosis. More than 95% of tuberculosis cases and deaths occur in resource-poor countries of the less-developed world. The diagnosis of tuberculosis mostly relies on tuberculin skin test, chest radiography, culture, and smear microscopy. Sputum smear microscopy is the most widely used technique for the diagnosis of pulmonary TB (PTB) especially in high prevalence countries. For effective TB detection, it is essential to assure the quality of smear microscopy. Quality Assurance (QA) is a system designed to continuously improve the reliability and efficiency of laboratory services. Panel testing, one of the QA systems that can provide data on laboratory capabilities and assess the current status of laboratory performance and detect problems associated with diagnostic performance. This study aims to prepare panel slides using three different methods, evaluate the efficiency of AFB smear microscopy in different laboratories in Ethiopia and the proficiency of peripheral laboratory technicians following training. Until now panel slides have been prepared by two methods. The methods use AFB appositive and negative sputum samples treated with sodium hydroxide (NaOH) and N-acetyl- L-cysteine (NALC). The third procedure of preparation of sputum smear slides for panel testing using new artificial sputum preparation method was developed and examined using a cultured monocyte cell line, cultured avirulent mycobacteria and methyl cellulose(MC) or polyacrylamide gel (PAM) for viscosity and background. Since it is expensive and tedious to grow monocytes in the laboratory we used pus drawn from acute abscesses in patients admitted to St. Paul hospital. Panel slides were prepared using the above three methods and compared. Slides prepared using NaOH were consistent with positivity grades but were not similar with real direct sputum smears macroscopically or microscopically. But slides made using PAM and MC were consistent with panel positivity grades and were similar to real direct sputum smears. Slides made with the three methods were found as they can be used for EQA and training in tuberculosis laboratories and microscopy centers. The slides were sent to 56 laboratories in the country to assess the performance of laboratory technicians. The result shows that the personnel were proficient enough to detect positive smears. A total of 29 technicians were trained and tested. Their results show that there was definite improvement after training. The results before training show that there is a high possibility of false negativity as a result of low performance of laboratory technicians. So panel slides have significant importance in assessing the performance of laboratory technicians and evaluating their proficiency before and after training. Moreover since the efficiency of lab technicians has significant effect on smear microscopy result, continuous external quality assessment has to be conducted using methods like panel slides.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	External quality assessment, panel test, validity, Mycobacterium tuberculosis
Subjects:	Q Science > QH Natural history > QH301 Biology Q Science > QR Microbiology R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine
Divisions:	Africana
Depositing User:	Selom Ghislain
Date Deposited:	04 Oct 2018 12:01
Last Modified:	04 Oct 2018 12:01
URI:	http://thesisbank.jhia.ac.ke/id/eprint/6743

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