The Platelet Count Can Predict In-hospital Death in HIV-negative Smear-positive Pulmonary Tuberculosis Inpatients

Objective This retrospective cohort study investigated whether the three components of the blood cell count have prognostic implications in HIV-negative Japanese adult inpatients with smear-positive pulmonary tuberculosis. Methods We reviewed patients who were treated by the isoniazid, rifampicin, pyrazinamide, and ethambutol regimen or by the isoniazid, rifampicin, and ethambutol regimen. The association between the patient data on admission and the survival outcome was evaluated. Results We reviewed 367 consecutive patients (male, 60.5%) with a median age of 72 [interquartile range (IQR), 54-82] years. While the white blood cell count did not differ between the two groups, (discharged alive: 7,000/μL; IQR, 5,500-9,300; died in hospital: 7,200/μL; IQR, 5,600-9,400; p=0.797), hemoglobin level (discharged alive: 11.5 g/dL; IQR, 10.0-13.1; died in hospital: 9.9 g/dL; IQR, 8.6-11.3; p<0.001) and the platelet count (discharged alive: 275,000/μL; IQR, 206,000-345,000; died in hospital: 149,000/μL; IQR, 93,000-236,000; p<0.001) were lower in patients who died in hospital. After dividing patients into hemoglobin- and platelet-based quantiles, the lower quantile class tended to show poorer survival (log-rank test for trend p<0.001 for both). A multi-variable Cox proportional hazards model revealed that hazard ratio for in-hospital death for every 1,000/μL increase of platelet count was 0.997 (95%CI, 0.995-0.999; p=0.010); the hazard ratio for the hemoglobin level was not significant. Conclusion A low platelet count was clearly related to a poor life prognosis in HIV-negative Japanese adult inpatients with smear-positive pulmonary tuberculosis.