After a spur-of-the-moment decision to apply for the AMSI Vacation Research Scholarship, this student learned about a long-known condition in horses that was well due for improvement in diagnostic clarity. The supplementary work performed is in support of some significant work in improving the accuracy and precision of clinical diagnosis of pituitary gland dysfunction in horses, allowing earlier diagnosis and treatment, potentially minimising injury and distress to the afflicted horses.
The start of my AMSI Vacation Research Project was rather sudden. On the last day of applications, at about 11:30am, one of my unit co-ordinators asked me if I’d like to do a summer research project about horses. Having an interest in biostatistics, and being something of a country kid, I accepted. Within an hour and a half, the application was in, and I had already started reading into the related biological phenomena. I learned about hormone regulation in horses, and how it can be affected by a condition known as pituitary pars intermedia dysfunction, or PPID. I learned about prevalence of a debilitating inflammatory condition called laminitis, and how it occurs far more frequently in horses with PPID. I learned about the data I was given, the technique I was using, and what the results could imply.
PPID is a degradation of the tissue separating the segments of the pituitary gland, resulting in the pars intermedia (the “middle part”) enlarging, and producing excess hormones which regulate cortisols. High levels of cortisols present in the body for a long period of time can have a number of effects, the most significant being suppression of the immune system. This leads to chronic episodes of laminitis, which can be quite painful and distressing to the affected horse or pony. PPID is also incurable, but manageable, especially so if caught early.
The most common diagnosis technique for PPID is to take a blood sample and test regulatory hormone levels. Hormone levels vary naturally throughout the year which can actually improve the confidence of diagnosis—there is a natural spike in hormone levels in autumn, which is much larger if the horse has even very minor PPID. But this could mean waiting up to ten months to resample if the result was inconclusive. Early diagnosis is quite important for PPID, so how can the diagnosis be improved?
My research project aimed to justify the usage of a robust statistical measure in defining clinical thresholds for typical hormone concentrations. The paper by Durham, Clarke, Potier and Hammarstrand, currently undergoing review for publication, uses this robust measure to define a set of clinical thresholds across an entire year, and with a weekly temporal resolution. This means that, spanning the entire year, a clinical threshold for diagnosis is defined for each individual week. This is a significant improvement over the previous model, which divided the year broadly as “autumn” or “not autumn”. Furthermore, these thresholds can now be defined with greater accuracy and precision than previous measures used, hopefully leading to earlier and more confident diagnosis of PPID.
Durham, A., Clarke, B. R., Potier, J., and Hammarstrand, R. (n.d.), `Temporally specific diagnostic thresholds for plasma ACTH in the horse’, Equine Veterinary Journal. Manuscript submitted for publication.