Infrared spectroscopy of synovial fluid as a potential screening approach for the diagnosis of naturally occurring canine osteoarthritis associated with cranial cruciate ligament rupture

Objective To evaluate infrared (IR) spectroscopy of synovial fluid (SF) as tool to differentiate between knees of dogs with naturally occurring OA associated with cranial cruciate ligament rupture (CrCLR) and controls. Method 104 adult dogs with CrCLR (affected group) and 50 adult control dogs were recruited in a prospective observational study. Synovial fluid (SF) samples were collected preoperatively from dogs with CrCLR and from a subset of these at 4-, and 12-week post-surgery. Knee samples were collected bilaterally once from control dogs. Dried synovial fluid films were made, and IR absorbance spectra acquired. After preprocessing, partial least squares discriminant analysis (PLS-DA) and ANOVA-simultaneous component analysis (ASCA) were used to evaluate group and temporal differences, and to develop predictive models. Results There were statistically significant spectral differences between the SF of OA affected and control dogs at all three time-points (P < 0.001). Pairwise comparison of spectral SF of knees with CrCLR over time showed statistically significant differences amongst all three time-points (P < 0.001). The predictive model for identifying the affected group from control had sensitivity, specificity and overall accuracy of 97.6%, 99.7% and 98.6%, respectively. Conclusions The findings demonstrate the ability of FTIR-spectroscopy of synovial fluid combined with chemometric methods to accurately differentiate dogs with OA secondary to CrCLR from controls. The role of this IR-based screening test as a diagnostic and monitoring biomarker for OA specific to the joint being sampled warrants further investigation.