What criteria should be used to assess troponin assays?

E. Smith has pointed out that the use of cryocrit in the investigation of cryoglobulinemia has analytical and clinical limitations, an observation with which we concur in general. The emphasis of our case study, however, was not to make a judgment on which technique should be used, but rather to focus on the importance of including cryoglobulin analysis in the differential and to address the need for standardization between laboratories. We reported a schema of sample collection and analysis that merely reflects a practice that many laboratories still conduct today. Vermeersch et al. reported that up to 37% of the 140 surveyed laboratories included cryocrit or other estimates (e.g., total protein) in their patient reports (1 ). The lack of standardization of practice appears, at least in part, to be related to a difference in opinion on the usefulness of estimating cryoglobulin quantities. Although some investigators reported no relationship between cryoglobulin concentration and the severity of symptoms and disease activity (2 ), cryoglobulin concentrations have, nevertheless, been found to correlate with response to treatment with plasmapheresis, cytotoxic agents, and/or interferon (3 ). Moreover, we did indicate in our report that cryocrit does not differentiate type 1 and type 2 cryoglobulinemia, and we recommended that serum protein electrophoresis and immunofixation should be conducted on resolubilized cryoprecipitate (4 ). Certainly, laboratories that do not have specialized equipment or a test in place to screen for cryoglobulins should consider at minimum estimating the cryocrit.