Moretto, L., Lavaud, A., Suter, A., Günther, C., Pot, S., & Glaus, T. (2021). Reliability of detecting fundus abnormalities associated with systemic hypertension in cats assessed by veterinarians with and without ophthalmology specialty training. Journal of feline medicine and surgery, 23(10), 921–927. https://doi.org/10.1177/1098612X20983265
https://journals.sagepub.com/doi/abs/10.1177/1098612X20983265
Systemic hypertension (SHT) is a widely recognized problem in geriatric cats. It can present idiopathic (no known underlying cause) or secondary to such common ailments as chronic kidney disease, hyperthyroidism, and hyperaldosteronism. Persistent elevated blood pressure (BP) in cats can cause damage directed at the eyes, brain, kidneys, and heart, a phenomenon known as target organ damage. While hypertensive damage is generally reversible, many cats present to their vet in advanced stages of target organ damage that results in a poor prognosis for recovery. Current veterinary guidelines suggest routine screening of BP in cats >10 years old or those being managed for a disease known to cause hypertension. Unfortunately, many general practice veterinarians, especially newer grads, feel inadequate at diagnosing target organ damage on a fundoscopic exam and thus prefer a referral to an ophthalmologist.
The purpose of this study was to evaluate the reliability of fundoscopic exams for identifying target organ damage in cats with SHT performed by a new graduate veterinarian without ophthalmology specialty training.
This was a case study of client-owned cats at the University of Zurich, Switzerland. Cats were initially considered for enrollment if they had a primary presenting complaint suggestive of SHT and an average systolic BP >160mmHg as measured by indirect Doppler sphygmomanometry.
The new graduate performed a fundic exam first using standard indirect ophthalmoscopy, followed by the ophthalmologist using more advanced equipment. The ophthalmologist’s detection of lesions was considered the gold standard comparison against which the new graduate was measured.
33 cats were enrolled, and 27 of those were diagnosed as being truly hypertensive based on the presence of target organ damage or subsequent elevated BP. Six of the cats had acute blindness, Nine had neurologic signs, and 12 had only persistently elevated BP. The remaining six cats from the original 33 were kept on as negative controls because their elevated SHT was not supported on subsequent BP measurements. The new grad detected fundus lesions in all six of the acutely blind cats, a sensitivity of 100%. In cats where the primary complaint was neurologic signs or SHT, sensitivity by the new grad dropped to 72%. The new grad did not detect any lesions in cats that the ophthalmologist declared free of lesions, a specificity of 100%.
There were two main limitations for this study other than the small sample size. Firstly, fundic lesions can result from other issues besides elevated BP, so there is no conclusive proof that the lesions identified were secondary to SHT. Secondly, the ophthalmologist’s opinion was set as the gold standard against which the new grad was compared, but specialists are imperfect and thus capable of missing lesions themselves.
Fundic exams by non-specialist veterinarians have reasonably high reliability for the detection of ocular target organ damage. Private practice vets are encouraged to perform an initial fundic exam in suspected hypertensive cats to help guide treatment and allow for earlier detection of damage. It should also be noted that a training effect was observed in this study, where the new grad’s sensitivity improved over time. This shows that while reliability may be lower initially, the primary obstacle for detecting fundic lesions is the will to actually perform a thorough fundic exam. -SdW
See also
ISFM Consensus Guidelines on Feline Hypertension
Related Blog Posts
https://everycat.org/cat-health/survival-study-after-diagnosis-of-feline-hypertension/
https://everycat.org/cat-health/biomarkers-of-feline-hypertension/