Some risk factors for death from TB have already been revealed, these include old age, dehydration, respiratory failure, decreased activity of daily living, and malnutrition .
However, much still remains to be clarified.
Although the blood cell count has different meanings depending on the clinical background, leukocytosis most commonly implies elevated inflammation due by bacterial infection, while a decreased hemoglobin level suggests iron deficiency and chronic inflammation, and a low platelet count indicates a high risk of bleeding.
In addition, recent studies have revealed that―in addition to white blood cells - platelets are involved in the defense mechanism .
Thus, a low platelet count might indicate the lack of a proper immune system.
To the best our knowledge, this is the first study to evaluate whether the three components of the blood cell count have prognostic implications in HIV-negative Japanese inpatients with smear-positive pulmonary TB.
Among the three components, the platelet count was the only marker that predicted in-hospital death.
The present study was associated with some limitations.
First, it was retrospective in nature, which might have induced bias. However, we believe that this simple study using a hard endpoint was not strongly biased by the study design.
Second, our TB cohort mainly consisted of elderly individuals that reflected the East Asian epidemiology .Thus, the findings should be validated in other cohorts, especially cohorts with younger patients, in the future.
Third,our data showed that a low platelet count was related to TB death.
However, the true causative factor of death among the patients with low-platelet counts was unclear.