The accuracy of ACTH as a biomarker for pituitary pars intermedia dysfunction in horses: A systematic review and meta-analysis.

BACKGROUND: Accuracy of baseline ACTH for the diagnosis of PPID in horses varies between studies. OBJECTIVES: To estimate the diagnostic accuracy of ACTH as a biomarker for PPID in adult horses and appraise potential causes of heterogeneity. STUDY DESIGN: Systematic review and meta-analysis. METHODS: A literature review identified studies reporting diagnostic accuracy data for extraction. Risk of bias was evaluated using QUADAS-2. Two random-effects models, the hierarchical summary receiver operating curve (HSROC) and the bivariate binomial normal model (BBN) were used to pool accuracy measurements. We performed meta-regression using study-level variables. The impact of diagnostic test accuracy on the frequency of false-positive and false-negative results at various pretest probabilities was calculated using the BBN model's accuracy results. RESULTS: Patient selection and index test evaluation demonstrated significant risk of bias. Mean and 95% confidence intervals for sensitivity and specificity for all studies (n = 11) based upon the HSROC model were (0.72, 95% CI: 0.62 to 0.82) and (0.88, 95% CI: 0.79 to 0.93), respectively. When studies with a common positivity threshold of 35 pg/mL ACTH were evaluated (n = 6), sensitivity and specificity were (0.66, 95% CI:0.54 to 0.77) and (0.87, 95% CI: 0.74 to 0.94). In a hypothetical group of one thousand horses with PPID prevalence of 2%, 20%, and 90%, the frequency of resulting false-positive and false-negatives would be (127 and 7), (104 and 68) and (13 and 306), respectively. Factors leading to increased accuracy were case-control design, clinical reference standard and data-driven choice of ACTH threshold. MAIN LIMITATIONS: A small number of primary studies (n = 11) were available, demonstrating significant biases. CONCLUSIONS: Less biased studies examining diagnostic accuracy of ACTH are needed. In horses with a high pretest probability of PPID, ACTH may be a functional "rule-in" test. Baseline ACTH is not recommended for screening purposes or use in horses without clinical signs of PPID.

A retrospective study of bronchoalveolar lavage fluid analysis in barrel racing horses with exercise-induced pulmonary hemorrhage and asthma in Texas from 2016 to 2018.

Exercise-induced pulmonary hemorrhage (EIPH) and asthma in barrel racing horses is a common disease across the United States. Limited information is available on non-infectious respiratory diseases in this population, the interaction between these two diseases, and the occurrence of both EIPH and asthma in the horse. The purpose of this study was to evaluate the bronchoalveolar lavage (BAL) fluid cytological results of barrel racing horses with EIPH, asthma, or both. A retrospective study was conducted using the medical records of horses that presented with cough and decreased athletic performance and BAL results that met the criteria for inclusion. Data from 95 horses were included from a private practice referral hospital in Texas. No statistical difference was found in the frequency of neutrophilia, eosinophilia, or mastocytosis between diagnoses of EIPH, asthma, or concurrent diagnoses of EIPH and asthma. Bronchoalveolar lavage of horses suspected of EIPH is warranted to fully characterize the noninfectious respiratory disease of barrel racing horses.