Veterinary Diagnostic Immunohistochemistry: A Survey of 47 Laboratories

Abstract

Forty-seven veterinary diagnostic laboratories (37 in the United States, 5 in Canada, and 5 overseas) participated in a survey of immunohistochemical (IHC) testing. The survey had three sections: 1) general, 2) type of tests, and 3) laboratory practice and quality assurance/quality control. Most laboratories performed THC for both diagnostic and research purposes. The number of testslyear ranged from <100 to >20,000 (most frequent range, 1000–5000). Most respondents expected the number of IHCs to increase. More than 60% coisidered IHC at least as relevant as other ancillary tests. About half the laboratories charged a fee per IHC test; the rest included IHC costs in the histopathology fee. The fee per test ranged from less than 10 to more than 30, with 75% of laboratories charging a fee of 11–30. All laboratories used formalin-fixed, paraffin-embedded samples routinely and frozen sections or tissues fixed in other fixatives much less frequently. Forty-three percent of laboratories performed IHC both for infectious and neoplastic diseases. Prion protein, bovine viral diarrhea virus, porcine reproductive and respiratory syndrome virus, and West Nile virus were the most common infectious diseases tests. The most common tests for cell markers were cytokeratins, virnentin, and CD3. Only four laboratories (two in the United States. one in Canada, and one overseas) had IHC procedures that followed IS0 17025 standards. Standardization of a test typically included checkerboard titrations of antisera, different antigen retrieval procedures, and known-positive tissue controls. A negative serum control was included for each specimen in <50% of laboratories. In approximately 45% of laboratories, a designated pathologist interpreted IHC results. IHC results were reported in different ways, including positivelnegative, detectedlnot detected, or a brief discussion of the results. More than 60% of laboratories reported IHC results within 1 week of the request; 33%, within 2 days. Most respondents agreed with the need for establishing IHC standards among different laboratories. This first comprehensive survey on IHC testing in veterinary diagnostic laboratories reveals a wide variety of tests in IHC and a strong interest in this technique. (The J Histotechno 1 28:19, 2005)Submitted: May 12, 2004; Accepted with revisions: September 28, 2004