Trilostane monitoring in canine hyperadrenocorticism: can basal cortisol replace the ACTH stimulation test?

PICO question In dogs with hyperadrenocorticism that are being treated with trilostane, does the measurement of basal cortisol levels have comparable diagnostic performance to the adrenocorticotropic hormone (ACTH) stimulation test? Clinical bottom line Category of research question Diagnosis (effectiveness of treatment monitoring) The number and type of study designs reviewed Four cross-sectional diagnostic accuracy studies were critically reviewed Strength of evidence Weak to moderate (level 2) Outcomes reported There is evidence of moderate strength suggesting that basal cortisol measured at 4–6 hours (and possibly 2–3 hours) post-trilostane can be a good test to exclude adrenal oversuppression, while its use is not suggested for diagnostic confirmation of oversuppression. There is evidence of weak strength that basal cortisol might be helpful for identifying dogs with inadequate adrenal suppression, but cannot be used to rule it out Conclusion Although the evaluation of the available evidence is difficult due to its heterogeneity, there is moderate evidence that a basal cortisol measured at 4–6 hours (and possibly 2–3 hours) post-trilostane dose can be a good test to rule out adrenal oversuppression, but that it cannot be used to definitively diagnose oversuppression. The current evidence suggests that basal cortisol is less useful for identification of inadequate control. Based on one included study, neither ACTH-stimulated nor basal cortisol levels correlate optimally with the actual clinical response of the patient. In this context, it can be concluded that none of the currently used laboratory tests should be used as a sole monitoring tool in dogs with hyperadrenocorticism receiving trilostane and thus, the assessment of the clinical response is of utmost importance How to apply this evidence in practice The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources. Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.