Validation of PLASMIC score in a cohort of patients with suspected thrombotic microangiopathy in an academic medical centre

Abstract

Background - The PLASMIC score is a rapid and inexpensive clinical assessment tool for predicting severe ADAMTS13 deficiency (<10% activity) in patients with suspected thrombotic thrombocytopenic purpura (TTP). The score includes 7 parameters: absence of active cancer, patient not having received stem cell transplant or organ transplant, platelet count <30×10⁹/L, haemolysis, mean corpuscular volume <90 fl, International Normalized Ratio <1.5, and serum creatinine <2 mg/dL.
Materials and methods - In this retrospective study, we evaluated a cohort of 59 consecutive patients with suspected thrombotic microangiopathy who had been referred to the Hemostasis and Thrombosis Center of the “Federico II” University of Naples, Italy, for measurement of ADAMTS13 activity. Relevant clinical and laboratory information were collected for all patients.
Results - The PLASMIC score was calculated in 52 of the 59 patients included in the study. In the high-risk group (PLASMIC score 6 or 7), 12 out of 20 patients (60%) had ADAMTS13 <10%. Interestingly, all 6 patients (100%) with PLASMIC score 7 had ADAMTS13 <5%. In the intermediate risk group (score 5), only one case out of 17 (5.9%) had ADAMTS 13 <10%. In the low-risk group (score 0-4), none of the patients had severe ADAMTS13 deficiency. The collected data enabled the sensitivity and specificity of PLASMIC score in TTP to be calculated, achieving 92% (95% CI: 0.80-0.98) and 79% (95% CI: 0.66-0.89), respectively. The PLASMIC score was seen to be a very efficient tool in distinguishing between patients with severe ADAMTS13 deficiency from those without, with an AUC of 0.92 (95% CI: 0.82-1.0; p<0.001).
Discussion - In our cohort, a high-risk PLASMIC score successfully predicted patients with severe ADAMTS13 deficiency, allowing the clinician to quickly define the best therapeutic approach, especially useful for those clinicians not used to the diagnosis and treatment of thrombotic microangiopathies.