Correspondence 705 Armand van Deun # Christopher Gilpin** Paul R. Klatser* *Royal Tropical Institute KIT Biomedical Research Amsterdam, The Netherlands † Centers for Disease Control and Prevention Division of TB Elimination National Center for HIV, STD, and TB Prevention Atlanta, Georgia ‡ University of Massachusetts UMASS Medical School Worcester, Massachusetts § Centers for Disease Control and Prevention Division of Laboratory Systems Public Health Practice Program Office Atlanta, Georgia, USA ¶ KNCV Tuberculosis Foundation The Hague, The Netherlands # International Union Against Tuberculosis and Lung Disease Paris, France **World Health Organization Stop TB Department Geneva, Switzerland e-mail: p.klatser@kit.nl http://dx.doi.org/10.5588/ijtld.11.0701 References 1 Martin R, Barnhart S. Global laboratory systems development: needs and approaches. Infect Dis Clin North Am 2011; 25: 677– 691. 2 Yao K, McKinney B, Murphy A, et al. Improving quality man- agement systems of laboratories in developing countries: an in- novative training approach to accelerate laboratory accredita- tion. Am J Clin Pathol 2010; 134: 401– 409. 3 World Health Organization/Centers for Disease Control and Prevention/Clinical Laboratory Standards Institute. Laboratory Quality Management System training toolkit 2012. Geneva, Swit- zerland: WHO, 2009. http://www.who.int/ihr/training/laboratory_ quality/en/index.html Accessed February 2012. 4 The Tuberculosis Coalition for Technical Assistance. Laboratory toolbox 2012. The Hague, The Netherlands: TB CAP, 2010. http://www.tbcta.org/Library/#232 Accessed February 2012. 5 NCCLS. Application of a quality management system model for laboratory services. Approved guidelines 3rd ed. Document GP26-A4. Wayne, PA, USA: NCCLS, 2011. 6 Gershy-Damet G M, Rotz P, Cross D, et al. The World Health Organization African Region laboratory accreditation process: improving the quality of laboratory systems in the African Re- gion. Am J Clin Pathol 2010; 134: 393– 400. Line probe and automated real-time PCR TB assays warrant adherence to strict quality assurance measures Direct molecular testing for laboratory diagnosis of tuberculosis (TB) can significantly reduce the turn- around time when compared with conventional meth- ods, and the technology has become routine in many laboratories in low-prevalence, high-income countries. The World Health Organization (WHO) has endorsed the use of two polymerase chain reaction (PCR) based commercial methods for TB: the line probe assay (LPA) for rapid detection of multidrug-resistant tuber- culosis (MDR-TB) in at-risk patients; and the auto- mated real-time PCR (RT-PCR) as an initial diagnostic test for MDR-TB or co-infected human immuno- deficiency virus (HIV) TB suspects, and in high-risk acid-fast bacilli (AFB) smear-negative suspects. 1,2 The WHO endorsement has resulted in broader imple- mentation of these tests in low-income countries with high burdens of TB. The accelerated rollout of LPA and RT-PCR addresses a critical need. However, to as- sure the reliability of testing, each laboratory should implement the following three measures: 1) use of a full set of controls, 2) confirmation of rifampicin (RMP) resistance when detected, and 3) participation in external quality assessment (EQA) programs. 1 The LPA and RT-PCR assays contain internal con- trols to detect inhibition of amplification. Neither of the tests, however, includes positive controls that would provide information on errors that may oc- cur during processing of specimens or DNA ex- traction, which could lead to false-negative results due to the loss of target bacteria or DNA. Controls should be run through the entire analytical cycle, beginning with specimen preparation. A positive control, containing an amount of mycobacteria near the lowest detection limit of the assay, will control for technical errors and fluctuations in re- agent quality. A negative control containing non- target DNA will monitor for cross-contamination. The recommended use of sterile water during PCR preparation as the only negative control will not indicate whether contamination has occurred during homogenization, sampling of specimens or DNA extraction. 2 It is well known that RMP-resistant tuberculosis has a significant impact on patient outcome. There- fore, it is imperative to confirm resistance, espe- cially in peripheral regions where staff may be inexperienced in interpreting or troubleshooting molecular assays. Discrepant results between mo- lecular and confirmatory testing should also be addressed, an issue that is not included in current WHO recommendations. 2 As removal of RMP is a very significant alteration to the standard treatment regimen, discrepant results such as those due to the presence of silent mutations or mutations asso- ciated with low levels of resistance to RMP should be resolved. 3 In addition, monoresistance to RMP, an emerging challenge in certain high-burden set- tings, should be ruled out before any modification in treatment. 4 3 Blinded rechecking of subsets of specimens should be implemented in each laboratory when the mo- lecular tests are introduced. A standardized EQA program for the LPA and/or RT-PCR is not yet available, but recent reports of false RMP resis- tance with RT-PCR 5 indicate that the development of such a system should be an urgent priority.