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Agreement in histologic assessments of the pituitary pars intermedia in aged horses

Dianne McFarlaneDepartment of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.

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Lisa M. MillerDepartment of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.

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Linden E. CraigDepartment of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Noel O. DybdalGenentech, 1 DNA Way, South San Francisco, CA 94080.

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Perry L. HabeckerDepartment of Pathobiology, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.

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Margaret A. MillerDepartment of Veterinary Pathobiology, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.

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Jon S. PattersonDepartment of Pathobiology, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

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Alastair E. CribbDepartment of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.

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Abstract

Objective—To evaluate concordance among veterinary pathologists in the assessment of histologic findings in the pars intermedia of pituitary gland sections from aged horses with mild signs suggestive of pituitary pars intermedia dysfunction (PPID).

Sample Population—10 pituitary glands from aged horses.

Procedure—7 pathologists were provided with signalment, clinical signs, and a single H&E-stained pituitary gland section from 10 aged horses with mild signs suggestive of PPID. Pathologists described histologic findings for each section and stated whether findings were consistent with PPID. Agreement among pathologists and with antemortem diagnostic test results was calculated.

Results—Overall, only fair agreement was found among the pathologists as to which horses had histologic findings consistent with disease (mean ± SE kappa value, 0.34 ± 0.069). Interpretation of individual sections varied, with minimal agreement (4 or 5/7 pathologists) for 5 of 10 sections evaluated. Postmortem assessment was in agreement with an antemortem endocrine diagnostic test result 79% of the time.

Conclusions and Clinical Relevance—Validation of antemortem diagnostic testing for PPID in horses often relies on the results of postmortem histologic evaluation. The lack of consensus in histologic interpretation of pituitary glands from aged horses with mild clinical signs in our study indicates that postmortem histologic evaluation of pituitary glands is an inappropriate standard in validation of antemortem diagnostic tests for detection of early PPID. Caution should be used when interpreting diagnostic test results in horses in which early PPID is suspected. (Am J Vet Res 2005;66:2055–2059)

Abstract

Objective—To evaluate concordance among veterinary pathologists in the assessment of histologic findings in the pars intermedia of pituitary gland sections from aged horses with mild signs suggestive of pituitary pars intermedia dysfunction (PPID).

Sample Population—10 pituitary glands from aged horses.

Procedure—7 pathologists were provided with signalment, clinical signs, and a single H&E-stained pituitary gland section from 10 aged horses with mild signs suggestive of PPID. Pathologists described histologic findings for each section and stated whether findings were consistent with PPID. Agreement among pathologists and with antemortem diagnostic test results was calculated.

Results—Overall, only fair agreement was found among the pathologists as to which horses had histologic findings consistent with disease (mean ± SE kappa value, 0.34 ± 0.069). Interpretation of individual sections varied, with minimal agreement (4 or 5/7 pathologists) for 5 of 10 sections evaluated. Postmortem assessment was in agreement with an antemortem endocrine diagnostic test result 79% of the time.

Conclusions and Clinical Relevance—Validation of antemortem diagnostic testing for PPID in horses often relies on the results of postmortem histologic evaluation. The lack of consensus in histologic interpretation of pituitary glands from aged horses with mild clinical signs in our study indicates that postmortem histologic evaluation of pituitary glands is an inappropriate standard in validation of antemortem diagnostic tests for detection of early PPID. Caution should be used when interpreting diagnostic test results in horses in which early PPID is suspected. (Am J Vet Res 2005;66:2055–2059)