The clinical diagnosis of equine sarcoids - Part 1: Assessment of sensitivity and specificity using a multicentre case-based online examination.
Authors: Koch C, Martens A, Hainisch E K, Schüpbach G, Gerber V, Haspeslagh M
Journal: Veterinary journal (London, England : 1997)
Summary
Clinical diagnosis of equine sarcoids relies heavily on visual assessment, yet the accuracy of this approach had never been formally validated until Koch and colleagues conducted a multicentre examination involving 181 veterinary professionals across four experience levels—from novices to recognised sarcoid experts—who reviewed 40 histologically confirmed cases (26 sarcoids, 14 other lesions) presented with standardised clinical information including photographs, signalment, lesion location, progression history and treatment response. The overall diagnostic success rate of 82.0% masks concerning variation in performance: whilst sensitivity and specificity were 83.3% and 79.6% respectively, less experienced practitioners frequently misdiagnosed lesions despite expressing high confidence in their judgement, suggesting overconfidence in clinical assessment is a particular risk in this cohort. The positive predictive value of 88.4% indicates that when clinicians diagnose a sarcoid they are usually correct, but the negative predictive value of only 72.0% reveals that roughly one in four lesions they dismiss as non-sarcoid may actually be sarcoid, potentially delaying treatment. For equine professionals, this research underscores the importance of histopathological confirmation—particularly when less experienced practitioners are involved in diagnosis—and supports the case for developing systematic diagnostic algorithms or biopsy selection tools that could reduce unnecessary treatments whilst catching true sarcoids that clinical assessment alone might miss.
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Practical Takeaways
- •Do not rely on clinical judgment alone for equine sarcoid diagnosis—even experienced clinicians misdiagnose ~17% of cases; always obtain histopathology for lesions where treatment is planned
- •High diagnostic confidence does not correlate with accuracy, particularly in less experienced practitioners; when uncertain, biopsy rather than treat empirically to avoid unnecessary morbidity
- •The high positive predictive value (88.4%) means if you think it's a sarcoid you're likely right, but the lower negative predictive value (72.0%) means a clinical 'not sarcoid' diagnosis is less reliable and should prompt biopsy if clinical doubt exists
Key Findings
- •Clinical diagnosis of equine sarcoids achieved 82.0% overall success rate with 83.3% sensitivity and 79.6% specificity across 181 veterinarians
- •Positive predictive value was 88.4% and negative predictive value was 72.0% in the tested population with 66% ES prevalence
- •Less experienced veterinarians frequently made incorrect clinical judgements despite high diagnostic confidence, indicating poor correlation between confidence and accuracy
- •Histopathological confirmation remains necessary as clinical assessment alone carries unacceptable diagnostic error rates for treatment decisions