Abstract
Aims: To investigate differences in anti‐cardiolipin antibody (aCL) testing and reporting practices among diagnostic laboratories participating in the RCPA Quality Assurance Program (QAP) Immunology Program.
Methods: A survey was sent to all 58 laboratories enrolled for aCL testing in the RCPA QAP Program requesting the following information: (1) manufacturer/type of assay; (2) isotype tested; (3) use of calibrators and controls; (4) whether calibrators, control and patient specimens were performed in singles or duplicates; (5) whether results were reported semi‐quantitatively and/or numerically; (6) values used to define negative/positive and semi‐quantitative cut‐offs and how they were determined; and (7) whether interpretative comments were provided and their content.
Results: Thirty‐two surveys (55%) were received. Significant differences were present particularly in the following areas: (1) whether IgM isotype aCL testing was performed routinely or only on specific request; (2) whether controls/calibrators/specimens were tested in singles or duplicates; (3) whether results were reported numerically and/or semi‐quantitatively; (4) the values used to define negative/positive and semi‐quantitative range cut‐offs; and (5) whether interpretative comments were provided and their content.
Conclusions: These differences in testing and reporting practices are likely to contribute to the variation in aCL results reported by different laboratories, particularly among those using the same assay.