Quality Assurance of Laboratory Tests for Tuberculosis

Chang-Ki Kim; Chulhun L. Chang

doi:10.5145/KJCM.2009.12.4.147

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Kim and Chang: Quality Assurance of Laboratory Tests for Tuberculosis

Original Article

Korean J Clin Microbiol 2009;12(4):147-153.

Published online: 22 December 2009

DOI: https://doi.org/10.5145/KJCM.2009.12.4.147

Quality Assurance of Laboratory Tests for Tuberculosis

Chang-Ki Kim¹, Chulhun L. Chang²

¹Korean Institute of Tuberculosis, Seoul, Korea

²Department of Laboratory Medicine, Pusan National University School of Medicine, Yangsan, Korea

Correspondence: Chulhun L. Chang, Department of Laboratory Medicine, School of Medicine, Pusan National University Yangsan Hospital, Yangsan 626-770, Korea. (Tel) 82-55-360-1870, (Fax) 82-55-360-1880, (E-mail) cchl@pusan.ac.kr

Received 17 August 20097 September 2009 Accepted 15 October 2009

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Clinical microbiology laboratories play a critical role in diagnosing tuberculosis (TB) and monitoring its treatment. Poor quality laboratory services remain a major barrier to diagnosis by microscopy and culture, and may complicate the interpretation of drug susceptibility testing (DST) results. External quality assessment (EQA) for microscopy is an important component of quality assurance, and includes panel testing, slide rechecking, and on-site supervision. Periodic panel testing is the simplest way to assess the performance of laboratories. Rechecking of a sample of routine smears by a higher-level laboratory is the method of choice for evaluation and continuous motivation of peripheral laboratories. On-site supervision allows the observation of workers’ performance under actual conditions, including equipment handling, laboratory safety, adequacy of supplies, and the processes used for smearing, staining, reading, recording, and reporting. Culture performance is not easily measured, and existing EQA programs are not sensitive enough to estimate the sensitivity of the process. Therefore, laboratory regulations and accreditation programs are critical to assure the quality of cultures. The Supranational Reference Laboratory Network (SRLN) was organized in 1994 to ensure optimal performance of laboratories conducting DST. A panel of 30 pretested and coded isolates is exchanged annually within the network for proficiency testing. It has been demonstrated that education and an EQA program can improve the proficiency of TB laboratories. However, quality programs in Korea are still weak. Expanded and strengthened laboratory quality improvement systems are necessary to achieve TB control in this country.

Keywords: Tuberculosis, Microbiology laboratory, Quality assurance, External quality assessment

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Table 1.

External quality methods used for AFB microscopy^∗

Method	Advantages	Disadvantages	Uses
On-site evaluation	Direct personal contact Motivating to staff Observation of actual work Identifies causes of errors Permits verification of equipment quality and function	Selective, usually not countrywide if left solely to the reference laboratory Labor intensive Costly	Always during supervisory visits Implement and monitor quality improvement measures Data collection and flow of information among laboratory levels Quarterly by district NTP supervisor At least annually by the reference laboratory
Panel testing	Low workload for peripheral center Improves laboratory credibility Rapid response countrywide possible Use of stained and unstained smears can help to identify source of problem May lead to identification of Faulty equipment	Does not measure routine performance High workload for central/reference laboratory May not be motivating to improve daily performance	Minimal first step for EQA with limited resources Rapid assessment of gross deficiencies Identify factors contributing to errors Assess training of microscopists
Blinded rechecking	Low workload for peripheral laboratory Motivates improved daily performance Reflects reality of routine performance	Heavy workload for higher level center Unavoidable inaccuracies Biased if not blinded Staff must be made available	Countrywide Standard for monitoring laboratory performance Ongoing and permanent

^∗ Table from reference[9].

Table 2.

Classification of errors^∗

Result being rechecked	Result of controller
Result being rechecked	Negative	Scanty	1+	2+	3+
Negative	Correct	LFN	HFN	HFN	HFN
Scanty	LFP	Correct	Correct	QE	QE
1 +	HFP	Correct	Correct	Correct	QE
2 +	HFP	QE	Correct	Correct	Correct
3 +	HFP	QE	QE	Correct	Correct

^∗ Table from reference[9].

Abbreviations: QE, quantification error; LFN, low false negative; LFP, low false positive; HFN, high false negative; HFP, high false positive.

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