Quality assurance of immunodiagnostic tests in Australia: II. Five year review

A Royal College of Pathologists of Australasia (RCPA) sponsored quality assurance program in clinical immunopathology has, over a 5 year period, demonstrated: enrollment by the majority of immunodiagnostic laboratories in Australia and New Zealand; improved compliance with the program over time eg. increasing numbers returning their replies by the due date; different commercial techniques give different mean values for the same analyte. This appears to be due to the use of different reference materials in each technique; greater utilization of nephelometric techniques in quantitating immunoglobulins, C3, C4, CRP and rheumatoid factor resulting in better accuracy and precision; improvement in the frequency of detecting anticentromere antibody as most laboratories use proliferating cell lines as substrate for anti-nuclear antibody (ANA) detection; improved interlaboratory concordance of ANA titers by the provision of reference standards; improved detection of antibodies to extractable nuclear antigens (counter-immunoelectrophoresis being more sensitive than immunodiffusion); the Farr and radioimmunoassay technique for the demonstration of antibodies to native DNA have greater sensitivity than the Crithidia assay; improvement in accuracy and precision of cell phenotype analysis with the use of whole blood and cell flow cytometric techniques; development of techniques to rank each laboratories performance on a rating scale based on the average number of tests outliers (from the consensus mean) per mailing. However deficiencies in performance are still being observed. These relate to both technical factors causing systematic errors and in the provision of interpretive comments on the laboratory result. Continuing education and participation in quality assurance programs are emphasized to monitor and improve performance over time.