Objectives:
To evaluate differences in clinical and laboratory features between primary and secondary immune-mediated thrombocytopenia (ITP), and to evaluate the diagnostic potential of these factors to differentiate between primary and secondary ITP.
Methods:
This single-center retrospective case-control study included dogs presenting with thrombocytopenia from 2014 to 2022, with a confirmed platelet count (PLT) <50x109/L. Dogs were excluded if a non-immune-mediated cause was detected, if other concurrent immune-mediated disease was present, in cases of insufficient work-up, and if immunosuppressive glucocorticoid treatment had been instigated for >12 hours. Dogs with ITP were categorized as secondary (sITP) if diagnostic work-up revealed an underlying cause and as primary (pITP) if no causative factor was found. Differences between disease groups regarding clinical signs of bleeding, PLT, and serum C-reactive protein (CRP) were examined.
Results:
47 dogs were included in the final population, with 14 classified as pITP and 33 as sITP. Dogs with pITP had a significantly higher occurrence of clinical bleeding (13/14) (P=0.003) and of a PLT<10x109/L (8/14) (P=0.037) compared to sITP ((15/33) and (7/33), respectively). Whereas dogs with sITP had a significantly higher occurrence of elevated serum CRP (>25 mg/L) (25/30) (P=0.049) compared to pITP (6/13). Lack of clinical bleeding was indicative of sITP (positive predictive value (PPV) =0.95) as was the combination of CRP>25 mg/L and PLT>10x109/L (PPV=0.88).
Impact:
Absence of clinical bleeding as well as a combined PLT>10 x109/L and elevated CRP>25 mg/L indicate that ITP is more likely to be secondary, thus making work-up for underlying disease more imperative.
Funding/Declaration of interests: None