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.