Thrombocytopaenia during methicillin-sensitive Staphylococcus aureus bacteraemia

The prognostic impact of thrombocytopaenia in Staphylococcus aureus bacteraemia (SAB) has previously been determined at bacteraemia onset only and relevant prebacteraemic thrombocytopaenia predisposing parameters have not been accounted for. We evaluated the prognostic impact of low thrombocyte count in SAB excluding prebacteraemic factors potentially causing thrombocytopaenia. This was a multicentre retrospective analysis of methicillinsensitive SAB (MS-SAB) patients. Thrombocyte count was determined at blood culture collection and at days 3 and 7. Thrombocytopaenia was defined as a thrombocyte count less than 150 × 109/L. Patients with chronic alcoholism, liver diseases and haematologic malignancies were excluded. Altogether, 495 patients were identified. Thrombocytopaenia at blood culture and at day 3 associated to endocarditis (p < 0.05 and p < 0.01) and defervescence (p < 0.001 and p < 0.01). Mortality at 90 days was higher for patients with thrombocytopaenia at blood culture collection (26 vs. 16%, p < 0.05), at day 3 (32 vs. 13%, p < 0.01) and at day 7 (50 vs. 14%, p < 0.001). In receiver operating characteristic analyses, thrombocytopaenia predicted a poor outcome at blood culture collection (p < 0.05), at day 3 (p < 0.001) and at day 7 (p < 0.001). When accounting for all prognostic parameters, thrombocytopaenia at day 3 [hazard ratio (HR), 1.83; p = 0.05] demonstrated a trend towards poor outcome, whereas thrombocytopaenia at day 7 (HR, 3.64; p < 0.001) associated to poor outcome. Thrombocytopaenia at blood culture collection was not a prognostic parameter when all prognostic factors were taken into account. However, hrombocytopaenia at day 3 indicated a poor outcome and thrombocytopaenia at day 7 was a significant independent negative prognostic marker that has not been previously reported in SAB