Usefulness of platelet count to predict concomitant valvular heart disease in patients with systemic lupus erythematosus

Background: Although the prevalence rate of valvular heart disease (VHD) is high in patients with systemic lupus erythematosus (SLE), the predictive factors of concomitant VHD have not been fully evaluated.

Methods and results: Among 288 patients with SLE who underwent transthoracic echocardiography at Kumamoto University Hospital from 2016 to 2021, 241 patients with sufficient echocardiographic data were retrospectively analysed. Among them, 22 (9 %) had VHD (10 had mitral regurgitation, 3 had aortic regurgitation, 6 had tricuspid regurgitation, 1 had mitral regurgitation and tricuspid regurgitation, and 2 had a prosthetic cardiac valve). After excluding the two patients with a prosthetic cardiac valve, we divided the remaining patients into two groups: the VHD group and non-VHD group. Multivariate logistic regression analysis revealed that age and the platelet count were significantly and independently associated with having VHD (age: odds ratio, 1.06; 95 % confidence interval, 1.02-1.10; p < 0.01) (platelet count: odds ratio, 0.99; 95 % confidence interval, 0.98-1.00; p < 0.05). After excluding 95 patients aged < 40 years, receiver operating characteristic analysis revealed that the area under the curve of the platelet count for prediction of VHD was 0.73 with an optimal cut-off value of 166.5 × 10³/µL (sensitivity: 76.6 %, specificity: 60.0 %). Among patients with a low platelet count (<166.5 × 10³/µL), the rate of having VHD was 29 % (12/41 patients). However, among those with a high platelet count (≥166.5 × 10³/µL), this rate was only 8 % (8/103 patients).

Conclusion: The platelet count is useful to predict concomitant VHD in middle-aged and older patients with SLE.