Program History and Background
In 1986, the Centers for Disease Control and Prevention (CDC) implemented the Model Performance Evaluation Program (MPEP) to evaluate the performance of laboratories conducting testing to detect human immunodeficiency virus type 1 (HIV-1) antibody (Ab). Since that time, the MPEP has been expanded to include the evaluation of performance for several other tests. Recently, due to changes in programmatic needs, the human T-lymphotropic virus types I and II (HTLV-I/II) antibody and HIV p24 antigen programs were discontinued.

The following table summarizes the history of the MPEP:

* T-lymphocyte Immunophenotyping - CD4 T-cell enumeration

Program Purpose
High-quality HIV-1 antibody testing is essential to meeting the public health objectives for the prevention and control of this retrovirus infection. High quality TLI and viral HIV-1 RNA (viral load) determinations are essential to HIV-infected patient care and management, and the mission of reducing retrovirus-associated morbidity and mortality. Prevention programs, diagnostic clinics, and seroprevalence studies rely not only on accurate antibody testing results to document HIV infection, but also accurate TLI, and HIV-1 viral RNA determinations. The impetus for developing this program came from the recognized need to assess the quality of retroviral and AIDS-related laboratory testing and to ensure that the quality of HIV-1 and HTLV-I/II Ab testing, TLI, HIV-1 viral RNA determinations, and HIV-1 p24 Ag testing was adequate to meet medical and public health needs. The objectives of the MPEP are to:

(1) Develop appropriate methods for evaluating quality in laboratory testing systems (including test selection, sample collection, and reporting and interpreting test results)

(2) Develop strategies for identifying and correcting testing quality failures

(3) Evaluate the effect of testing quality on public health.

Program Design
The MPEP is designed to analyze the steps in the total testing process and to identify the critical indicators of high-quality testing. Annually, the MPEP mails two performance evaluation sample panels each for HIV-1 Ab, TLI, and HIV-1 viral RNA. Participant laboratories are requested to test the performance evaluation (PE) samples that CDC mails them in the same manner they test routine clinical specimens, and to report their testing results to CDC on specially designed forms. Aggregate data are derived from the testing results of enzyme immunoassay (EIA), Western blot (WB), indirect immunofluorescence assay (IFA), radioimmuno-precipitation assay (RIPA), other tests, TLI cell counts and percentages, or copies of HIV-1 viral RNA, provided to CDC by each of the laboratories. CDC is responsible for compiling and analyzing the results and sends aggregate reports of testing results to all participant laboratories following each PE survey. In addition to sample panel surveys, participant laboratories are asked to complete a survey questionnaire every other year describing the characteristics of their laboratory and their testing practices.

The MPEP is not proficiency testing. The MPEP provides detailed analysis of aggregate data and does not grade results from individual laboratories. Graded laboratory proficiency testing surveys are conducted, for example, by the College of American Pathologists (CAP) and the American Association of Bioanalysts (AAB). Of the approximately 850 laboratories enrolled in the MPEP for HIV-1 Ab testing, nearly 80% are also enrolled in programs sponsored by CAP or AAB.

Participation
The PE surveys are provided free of charge to participant laboratories. The PE surveys depend upon a wide spectrum of laboratory participation to generate a representative data base. To accurately assess the quality of laboratory testing, we need the participation of laboratories representing all levels of performance. Past CDC experience has shown that participation in PE surveys leads to improved testing performance. By encouraging participation in the PE surveys, CDC is giving participant laboratories an opportunity for self-improvement and, in addition, a basis for developing prevention and intervention strategies. Interest in the program is quite high; approximately 90 percent of the laboratories receiving sample panels respond with results. This high rate of participation indicates strong support for achieving the goal of improving and maintaining high quality laboratory testing.

Recruitment for volunteer enrollment in the MPEP is ongoing by CDC (to date more than 17,000 laboratories have been contacted). Not all of the laboratories contacted perform HIV-1 Ab testing, TLI, or HIV-1 viral RNA determinations, but of those that do perform these tests and participate in the MPEP, approximately 850 perform HIV-1 Ab testing, 300 perform TLI and 225 perform HIV-1 viral RNA determinations.

Reports
The reports sent to participant laboratories following each PE evaluation survey consist of tables and graphical figures, grouped for each performance evaluation sample, by test kit manufacturer, test method, WB band patterns, and IFA intensity, for example. A written analysis of results accompanies each final report. Although the MPEP is not a regulatory program, laboratories find the aggregate reports of testing results beneficial in comparing their results with those from other laboratories. This practice affords each laboratory the opportunity for self-improvement and serves as a vehicle to accomplish an important objective of the MPEP: improving and maintaining high quality testing. Periodic brief reports highlighting important findings are sent to MPEP participants, usually after aggregate reports have been distributed. Reprints from CDC Morbidity and Mortality Weekly Report (MMWR) publications and from CDC authored peer-reviewed journal publications concerning retroviral or AIDS-related testing are also sent to participant laboratories.

Assessing Preanalytic and Post analytical Processes
To identify and assess barriers to high-quality laboratory testing in preanalytic and postanalytic steps of the total testing process for HIV-1 Ab, TLI, and HIV-1 RNA (viral load), CDC collaborates with the Association of Schools of Public Health and San Diego State University Graduate School of Public Health to develop systematic analyses for identifying variables in the steps of the testing process. These analyses are used to assist in cataloging events that occur from the time tests are requested through specimen collection, laboratory analyses, and reporting of test results so that potential problems, particularly in the preanalytic and postanalytic steps of the testing process, can be identified and corrected. Some of these analyses include:

- Examination the variability of viral load and CD4 T-cell testing laboratory reports and adherence to published testing guidelines.

-Identification of nonanalytic issues in HIV-1 antibody testing using blind proficiency testing.

-Use of a nominal group process for improving the performance of laboratories conducting HIV antibody testing

-Personnel competency assessments.

MPEP Focus on Laboratory Practices
Through PE survey data and ongoing research, the MPEP evaluates laboratory practices linked to high quality performance. The focus is on answering such questions as the following:

-What are the testing practices and characteristics of laboratories that test for HIV-1 Ab, perform TLI, or determine HIV-1 viral RNA?

-Do these practices affect quality in the laboratory testing process?

-Is the high quality of laboratory testing dependent upon the nature of the laboratory itself, e.g., public health versus blood collection center versus hospital-based laboratory versus independent laboratory, numbers of samples tested, types and sequence of tests performed, internal and external quality assurance procedures implemented throughout the testing process, education and training of testing personnel, or experience of personnel performing the testing?

-What strategies for correcting quality failures are most effective and how can they be implemented?

MPEP Products
Currently, we provide the following:

-Reports to participants: These reports contain graphical figures and analyses of the PE sample survey and questionnaire results, which are useful indicators in detecting performance deficiencies and quality results.

-Publications: MPEP Performance Bulletins addressing specific testing performance issues, MMWR articles describing specific aspects of performance results, and peer-reviewed journal publications directly addressing testing issues.

-Statistical analyses: Examination of participant laboratory data to develop a profile of the characteristics which distinguish a laboratory testing process that performs consistently well from one that performs poorly. This information is essential for targeting strategies for improving the quality of laboratory testing.

Future Plans
Future plans of the MPEP include:

(1) Refinements in existing programs, such as performance panels to evaluate new methods in HIV-1 Ab testing (particularly in the area of rapid testing), new or changing methods in performing TLI, and new methods in determining HIV-1 viral RNA

(2) Provision of online performance data submission

(3) Expansion of the survey design to broaden our knowledge about the level of quality in the preanalytic and postanalytic steps of the testing process

(4) Recommendations for intervention strategies for laboratory improvement.