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EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2022) 34 (2) 58-59 doi: 10.1111/eve.13613
Highlights of recent clinically relevant papers
Laryngeal function grade There is persistent concern among some trainers, owners and veterinarians regarding the effect of preoperative laryngeal function grade on the outcome of laryngoplasty and ventriculocordectomy (LPVC). The aim of this retrospective case series by Ali Broyles and co-workers based in the USA was to determine the effect of laryngeal function grade prior to LPVC on postoperative performance. Medical and race records of Thoroughbred racehorses
diagnosed with recurrent laryngeal neuropathy (RLN) and treated with LPVC at Rood and Riddle Equine Hospital between 1998 and 2013 were reviewed. Horses were placed into three groups based on preoperative laryngeal function grade (grade III.1, grades III.2/III.3, and grade IV). The effect of preoperative laryngeal function grade on postoperative performance was determined by multivariable logistic regression, Cox proportional hazard model and multivariable linear regression analysis. In a multivariable logistic regression, grade III.2/III.3 horses
had 1.88 times higher odds (95% CI: 1.03–3.43) of racing after LPVC than grade IV. A multivariable Cox’s proportional hazard analysis controlling for race prior to surgery showed that likelihood of racing postoperatively was not different between grade III.1 and grade IV. Kaplan–Meier survival analysis showed that grade IV horses took a longer time to race compared with grade III.1 and grade III.2/III.3. Laryngeal function grade did not influence the mean earnings per start. The main limitation was the small number of horses in the grade III.1 group (n = 68) compared with the III.2/III.3 (n = 313) and IV (n = 242) groups. Laryngeal function grade may affect likelihood of racing
after LPVC, but not earnings per start. Grade III.2/III.3 horses were more likely to race postoperatively than grade IV horses, and grade IV horses took a longer time to first race after LPVC.
ACTH as a biomarker for PPID
Accuracy of baseline adrenocorticotropic hormone (ACTH) for the diagnosis of pituitary pars intermedia dysfunction (PPID) in horses varies between studies. The aim of this systematic review and meta-analysis by James Meyer and co-workers in the USA and UK was to estimate the diagnostic accuracy of ACTH as a biomarker for PPID in adult horses or ponies and appraise potential causes of heterogeneity. A literature review identified studies reporting diagnostic
accuracy data for extraction. Risk of study bias was evaluated using QUADAS-2. To account for variations between studies, such as variable positivity thresholds, two random-effects models (the hierarchical summary receiver operating curve (HSROC) and the bivariate binomial normal model (BBN)) were used to pool accuracy measurements. Meta-regression was performed using study-level variables. The impact of diagnostic test accuracy on the frequency of false-positive and false-negative results at various pre-test probabilities was calculated using the BBN model’s accuracy 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) were 0.72 (95%
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CI: 0.62–0.82) and 0.88 (95% CI: 0.79–0.93), 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: 0.54–0.77) and 0.87 (95% CI: 0.74–0.94). In a hypothetical group of 1000 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. In horses with clinical signs 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. To minimise false negatives in horses with clinical signs of PPID, a negative ACTH test should be followed up with a thyrotropin-releasing hormone (TRH) stimulation test.
Pregnant broodmares with colic
This study by Hope Douglas and co-workers in the US evaluated, following colic admission during pregnancy, (1) broodmare survival; (2) the frequency of recurrent colic in broodmares and its associated variables, and (3) pregnancy outcome and the variables associated with a negative pregnancy outcome. Admissions of 104 pregnant mares over a 6-year period
were included. Cox proportional hazards regression analysis was performed to evaluate variables associated with broodmare survival. Logistic regression analysis was used to examine the variables associated with recurrent colic and pregnancy outcome. Broodmares from 73/104 (70.2%) admissions were
discharged alive. Lesion category, admission hyperlactataemia (hazard ratio (HR): 3.24; 95% CI: 1.28–8.22), and admission high packed cell volume (HR: 2.89; 95% CI: 1.29–6.47) were associated with reduced survival. Recurrent colic was observed in broodmares from 33/70 admissions (47.1%). The final multivariable model for recurrent colic included Thoroughbred breed (OR: 5.09; 95% CI: 1.58–16.4) and age (OR: 0.876; 95% CI: 0.747–1.03). Overall, negative pregnancy outcome was 14/65 (21.5%). Lesion category, evidence of systemic inflammatory response syndrome (SIRS) in hospital (OR: 31.2; 95% CI: 2.09– 466.5), and diarrhoea in hospital (OR: 379.3; 95% CI: 97.1–1482.0) were associated with increased negative pregnancy outcome. Altrenogest administration was inversely associated with negative pregnancy outcome(OR: 0.029; 95% CI: 0.004–0.222). Pregnant broodmares admitted for colic had lower
survival than anticipated and were at risk of recurrent colic. Markers of broodmare disease severity were associated with pregnancy outcome. Lesion category, haematologic variables (packed cell volume and l-lactate concentration), evidence of SIRS, and diarrhoea were useful for predicting broodmare and pregnancy outcomes.
Rope-assisted recovery
In this knowledge summary, Ffion Lloyd and Pamela Murison from the University of Glasgow, UK considered the PICO question ‘In horses undergoing general anaesthesia, does
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