Reduction of variation in results of rheumatoid factor tests by use of a serum reference preparation

Abstract

Standaridizing test results for rheumatoid factor by comparing results obtained for an unknown with results obtained for a serum reference preparation decreased variance between laboratories, as measured in the Center for Disease Control proficiency testing program, by 77%. The amount of improvement was also estimated by the type of test and by the manufacturer's product. Standardization resulted in an increase in the number of reported results that were within a twofold dilution of the median value. The percentage increased from 50.3 to 93.7% for the slide tests and from 78.1 to 91.2% fro the tube tests. Decrease in variance by manufacturer's product ranged from 94 to 27%. The study demonstrated that adopting a reference serum standard could substantially improve the comparability of rheumatoid factor test results and that proficiency testing programs can be used to estimate improvement which could be expected as a result of standardization.

Center for Disease Control Diagnostic Immunology Proficiency Testing Program results for 1977

“…Because there had been excessive variability in the rheumatoid factor test results from previous surveys, three specimens calibrated in international units (IU) for rheumatoid factor were included in the second-quarter shipment (19,22). Results were reported in the usual manner but were then converted to IU by comparing results of the first two specimens against the one containing 250 IU of rheumatoid factor per ml.…”

“…The rheumatoid factor standardization proficiency testing study (19) demonstrates that, whereas a proficiency testing program can be instrumental in improving laboratories by evaluating tests and methodologies ( 14), it can also encourage standardization and estimate *the amount of improvement that could be expected from standardization. To emphasize further the need for and value of standardization, a reference sample for rheumatoid factor will be included with future proficiency testing samples until other standards are readily available and commonly used.…”

Clinical Diagnostic Immunology in A Clinical Microbiology Laboratory

“…After the antigen and patient's serum have had time to react and take up the limited amount of compliment available in the system, the indicator system is added to show whether or not there is free complement. 17 Controls are included to ensure that none of the reagents are anticomplementary (able to take up complement nonspecifically as might, for example, occur with contaminated serum) and positive and negative control sera are tested in parallel. 18 These tests have wide applications in the diagnosis of bacterial and viral infections.…”

“…A negative reaction in an adult , particularly in one known to have previously shown a positive test , raises the possibility of a defect of the cellmediated immune system, which in the adult would likely to be secondary to some disease state affecting the lymphoid tissues such as Hodgkin's disease , multiple myeloma , Leukaemia and Lymphosarcoma. 17…”

“…Immunoblot analysis is a valuable confirmatory test for HIV antibodies and its use is being extended to the detection of many hospital pathogens. 17 5. Laser based flow cytometry which measures forward angle light scatter that is related to the size of cells being measured is increasingly used in immunology for the identification of cell populations (phenotyping) and for separation (sorting) on the basis of staining patterns with fluorescent ligands.…”