J. Rex Astles

Performance of Tuberculosis Drug Susceptibility Testing in U.S. Laboratories from 1994 to 2008

ABSTRACT We present a statistical summary of results from the Model Performance Evaluation Program (MPEP) for Mycobacterium tuberculosis Drug Susceptibility Testing, 1994 to 2008, implemented by the U.S. Centers for Disease Control and Prevention (CDC). During that period, a total of 57,733 test results for culture isolates were reported by 216 participating laboratories for the first-line antituberculosis drugs used in the United States—isoniazid (INH), rifampin (RMP), ethambutol (EMB), and pyrazinamide (PZA). Using Clinical Laboratory and Standards Institute (CLSI)-recommended concentrations for one or more of three methods, agar proportion (AP), BACTEC460 (Bactec), and MGIT-960 (MGIT), yielded overall agreement of 97.0% for first-line drugs. For susceptible strains, agreement was 98.4%; for resistant strains, agreement was 91.0%, with significantly lower accuracy (chi-square test, P < 0.0001). For resistant strains, overall agreement by methods was 91.3% for AP, 93.0% for Bactec, and 82.6% for MGIT and by drugs was 92.2% for INH, 91.5% for RMP, 79.0% for EMB, and 97.5% for PZA. For some strains, performance by method varied significantly. Use of duplicate strains in the same shipment and repeat strains over time revealed consistent performance even for strains with higher levels of interlaboratory discordance. No overall differences in performance between laboratories were observed based on volume of testing or type of facility (e.g., health department, hospital, independent). By all methods, decreased performance was observed for strains with low-level INH resistance, RMP resistance, and EMB-resistant strains. These results demonstrate a high level of performance in detection of drug-resistant M. tuberculosis in U.S. laboratories.

The State Public Health Laboratory System

This article describes the development since 2000 of the State Public Health Laboratory System in the United States. These state systems collectively are related to several other recent public health laboratory (PHL) initiatives. The first is the Core Functions and Capabilities of State Public Health Laboratories, a white paper that defined the basic responsibilities of the state PHL. Another is the Centers for Disease Control and Prevention National Laboratory System (NLS) initiative, the goal of which is to promote public-private collaboration to assure quality laboratory services and public health surveillance. To enhance the realization of the NLS, the Association of Public Health Laboratories (APHL) launched in 2004 a State Public Health Laboratory System Improvement Program. In the same year, APHL developed a Comprehensive Laboratory Services Survey, a tool to measure improvement through the decade to assure that essential PHL services are provided.

Laboratory Services in Support of Public Health: A Status Report

Objectives. To assess Healthy People 2010 Objective 23–13 and its related sub-objectives measuring comprehensive laboratory services in support of essential public health programs, the Association of Public Health Laboratories (APHL) collaborated with the Centers for Disease Control and Prevention (CDC) to create and administer a survey of state public health laboratories (PHLs). Methods. A committee of APHL, with representation from CDC, constructed the survey based on the 11 Core Functions of State Public Health Laboratories (hereafter, Core Functions)—the premise being that the extent to which they fulfilled these Core Functions would represent their level of providing or assuring comprehensive laboratory services in support of public health. The survey was distributed biennially to all state health agencies from 2004 to 2008, and respondents were given two months to complete it. Results. The response rate for all surveys was ≥90.2%. State PHLs were more likely to meet the sub-objectives relating to traditional functions (e.g., disease surveillance and reference testing) than other areas (e.g., food safety and environmental testing). Emergency preparedness fell in between. Overall, but most notably in the areas of food safety and training and education, there was improvement from 2006 to 2008, with the percentage of respondents who met more than half of the sub-objectives increasing from 58.7% in 2006 to 61.2% in 2008. Conclusions. The comprehensive laboratory services survey has been a valuable tool in measuring the laboratory infrastructure that underpins public health in the U.S. It will be necessary to continue monitoring laboratory infrastructure in this way to determine where the gaps in services exist and how they can best be addressed.

Systems Approach to Improving Antimicrobial Susceptibility Testing in Clinical Laboratories in the United States

ABSTRACT Laboratory practice in the preanalytical phase of antimicrobial susceptibility testing (AST) was evaluated in 102 hospital, reference, physician office-clinic, and public health laboratories in Washington state. Surveys were sent to evaluate (i) use of NCCLS/CLSI (formerly NCCLS) AST performance standards, (ii) technical competence in AST case studies, challenging knowledge of contemporary testing issues, and (iii) choice of antimicrobial agents to test for Streptococcus pneumoniae. Numerous deficiencies were identified in the survey: (i) initially only 40% of the laboratories surveyed used current NCCLS/CLSI AST performance standards, (ii) the rate of accurate responses for three different case studies ranged from 29% to 69%, and (iii) variation was noted in the choice of antimicrobials tested against invasive isolates of S. pneumoniae. These deficiencies could affect therapy and detection of antimicrobial resistance. Several educational programs were implemented to improve AST policies and practices, and a follow-up survey indicated that four intervention strategies were most effective: (i) regional technical workshops, (ii) National Laboratory Training Network teleconferences, (iii) use of the Centers for Disease Control and Prevention (CDC) CD-ROM on AST, and (iv) the CDC Multilevel Antimicrobial Susceptibility Testing Resource website. The interventions could be implemented more widely in the United States to improve AST knowledge and practices.