Abstract
The data accumulated from 1969 to 1979 in the Diagnostic Immunology portion of the Center for Disease Control Proficiency Testing Program were evaluated for evidence of change in performance among the participating laboratories. Evidence of improved performance was found for the rubella, rheumatoid factor, tularemia, quantitative immunoglobulin (immunoglobulin G, A, and M), and hepatitis B tests. No evidence of change was detected for the streptococcal enzyme, C-reactive protein, infectious mononucleosis, antinuclear antibodies, Salmonella and Brucella agglutinins, and syphilis tests. Data obtained from other tests were inadequate to determine trends. In most tests, deficiencies were identified which could be corrected and thereby could improve performance. It is pointed out that proficiency testing not only improves laboratory performance, but also can be used to evaluate performance levels, identify method, standard, or performance deficiencies, educate, estimate impact of possible changes, serve as external quality control, and document changes.