Evaluation of the application of computed tomography to assess bone mineral density using intrarater reliability and subsequently analyzing risk factors for decreased bone mineral density in Psittaciformes in the Netherlands

Abstract

Background and relevance: Captive psittacine birds living at higher latitudes (Northern Europe), experience significantly less sunlight compared to their native habitats, potentially leading to hypovitaminosis D and associated osteoporosis. Objective: The study aims to establish a reliable method for evaluating bone mineral density (BMD) in Psittaciformes using computed tomography (CT) imaging and to identify risk factors associated with decreased BMD. Relevance: Gaining insight into BMD, prevalence of osteoporosis and associated risk factors can help to improve captive care practices and reduce the prevalence of osteoporosis related health issues, thereby enhancing the welfare of captive Psittaciformes. Materials and Methods: BMD was measured in 65 psittacine birds at ten different bone regions using Hounsfield Units (HU) following a standardized protocol. Intrarater and interrater reliability were assessed using intraclass correlation coefficients (ICC). Additionally, information on husbandry practices and nutrition was collected to determine possible risk factors for decreased BMD. Results: Intrarater reliability was high for all anatomical locations except the trabecular tibiotarsus. After refinements of the protocol for the trabecular tibiotarsus, the interrater reliability was high. The interrater reliability was inconsistent, the measurements of the ulna being the worst. Only diagnosis, weight of the bird and genus showed significant results impacting BMD in a few bone regions. Conclusions: BMD is preferably measured by one rater to ensure consistent measurements. Further refinements could help to ensure greater interrater reliability. The study did not conclusively identify risk factors for decreased BMD. More data (larger sample size) is needed to draw definitive conclusions regarding risk factors for decreased BMD.