Anti-cardiolipin antibody testing and reporting practices among laboratories participating in a large external Quality Assurance Program.

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.