Hematological biomarkers such as red cell distribution width (RDW), mean platelet volume (MPV), mean corpuscular volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), or platelet (PLT) count are machine-calculated parameters derived from a complete blood count (CBC). These values have been demonstrated to be predictors of adverse clinical outcomes in patients.
For example, RDW following the adjusted hazard ratios (HRs) for all-cause mortality were strongly associated with an increased risk of death in middle-aged and older (11,827) adults, i.e. for every 1% increment in RDW, all-cause mortality risk increased by 22% (HR = 1.22, 95%CI: 1.15–1.30, P < 0.001) [1]. In addition, RDW was strongly associated with deaths in older adults from cardiovascular disease (CVD) (HR = 1.15, 95%CI: 1.12–1.25), cancer (HR = 1.13, 95%CI: 1.07–1.20), and other causes (adjusted HR = 1.13, 95%CI: 1.07–1.18) [2]. Association between RDW and all-cause mortality in chronic kidney disease (CKD) patients was also reported in [3].
Higher MPV as an indicator of larger and more reactive platelets has been associated with a higher risk of death in hemodialysis (HD) patients (all-cause mortality). Following [4] in nearly 150.000 incident HD patients higher MPV levels (> 11.5 fL) were associated with incrementally elevated death risk. In those patients it was also shown that an increase in mean platelet volume /platelet count (P) ratio was associated with vascular access failure (VAF) [5]. The authors reported that in multivariate Cox regression analysis, MPV/platelet count ratio remained a significant independent risk factor for VAF, even after adjusting for age, sex, diabetes, coronary artery disease, cerebrovascular disease, and vascular access type (HR = 1.16, 95%CI: 1.11–1.22, P < 0.001). MPV/P ratio was demonstrated to be a predictor of adverse outcome in non-ST-segment elevation myocardial infarction (NSTEMI) patients (the ratio is a useful marker to predict a long-term prognosis in NSTEMI patients undergoing percutaneous coronary interventions). Moreover, MPV/P ratio was similar to Global Registry of Acute Coronary Events (GRACE) score [6] but better than MPV for predicting all-cause mortality. Furthermore, it was easier to calculate than GRACE score.
Recently, MCV as a measure of average size of erythrocytes has been associated with mortality in many clinical settings. Elevated MCV (generally > 100 fL) is often characteristic of underlying conditions such as nutritional deficiencies, drug and alcohol use [7], vitamin B12 deficiency [8], certain medications or bone marrow disorders [9]. In patients with ≥ 3 chronic kidney disease (CKD) stages, MCV was associated with all-cause mortality, cardiovascular disease mortality, and infection-associated mortality [10]. Other authors [11] applied Cox regression analysis MCV to predict composite cardiovascular (CV) events in CKD patient as a major confounding factor. Based on the > 100 thous. incident HD patients and those with higher (> 98 fL) MCV levels, a higher all-cause cardiovascular and infectious mortality risk was also currently confirmed by [12]. A gradient relationship between increased MCV and deaths associated with cerebral ischemic stroke (CIS) and ischemic heart disease (IHD) was reported in Taiwanese investigators using a large-scale (66,294) population-based study [13]. In addition, [14] and [15] reported a positive relation of MCV with clinical response in patients with advanced solid malignancies and gastric cancer after chemotherapy with capecitabine.
We have found the fewest mortality reports for MCH and MCHC. Inverse associations between MCH and MCHC and all-cause mortality were observed among men, but not among women [16]. The study, however, was based on a relatively small number of participants (n = 403) and these findings warrant confirmation in further prospective studies conducted on a bigger population. In addition, lower MCHC is associated with poorer outcomes in intensive care unit admitted patients with acute myocardial infarction [17].
PLT count is a prognostic indicator in the general population and the elderly. However, the U-shaped relationship exists between platelet count and mortality (low PLT count is associated with cancer in the general population and high PLT count is associated with CVD) [18]. U-shaped mortality curve associated with platelet count was observed in the New York outpatient population of 36,262 individuals (≥ 65) [19] and among 131,308 Taiwanese older people (≥ 65) [20]. This finding was also confirmed by [21] in 3 population-based studies on 40,987 inhabitants of 7 Italian areas and [22] in 1797 international stable chronic obstructive pulmonary disease (COPD) patients within 3-year all-cause mortality observation.
In the above cited reports, relatively longer follow-ups of subjects were taken to estimate the risk and evaluate mortality. In contrast, acute deaths of such individuals have not been fully addressed.
Aim
In this paper, we present statistical results of an analysis of patients who were recently discharged from inpatient facilities within one month prior to the index emergency department (ED) visit. Using selected hematological biomarkers and routine statistical tools we predict acute mortality in Polish ED patients.