Curriculum in Cardiology
Routine hematologic clinical tests as prognostic markers in patients with acute coronary syndromes

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Prognostic markers are needed to identify patients with acute coronary syndrome (ACS) who are at high risk for adverse events. Although the search for new biomarkers is quite active, prognostic information is available from routine hematologic tests, such as the complete blood count. For example, elevated white blood cell counts during ACS are associated with increased risk of mortality, heart failure, shock, and left ventricular dysfunction. Anemia is associated with increased risk of mortality, whereas elevated platelet counts predict poorer clinical and angiographic outcomes. In this review, we summarize the literature regarding the use of clinical hematology tests including white blood cell count, hemoglobin and hematocrit values, and platelet count as prognostic markers in patients with ACS, and we describe potential mechanisms to explain these associations.

Section snippets

White blood cell count

Of all laboratory parameters reviewed, the most thoroughly investigated prognostic marker has been the WBC count. Because of the abundance of data, our review of the WBC count was restricted to primary clinical outcomes in trials with ≥2000 patients in the setting of ACS6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 (Table I). ACS refers a spectrum of clinical events including unstable angina and acute myocardial infarction (AMI), which is further divided into ST-segment elevation (STEMI) and

Hemoglobin and hematocrit

Table III lists the 9 largest studies whose primary goal was to investigate if a patient's hemoglobin or hematocrit value could be used as a prognostic marker during ACS.24, 25, 26, 27, 28, 29, 30, 31, 32 Of the studies reviewed, all except one24 displayed increased mortality in patients with lower hemoglobin or hematocrit values.

Five studies demonstrate that low hemoglobin and hematocrit values are associated with increased short-term mortality; 4 included patients with AMI,25, 26, 27, 29 and

Platelet count

Both elevated and depressed platelet counts are associated with adverse clinical outcomes. Patients with essential thrombocytosis are at higher risks for developing coronary thrombosis, even in the absence of a coronary atherosclerotic plaque, because of increased platelet activation and increased blood viscosity.44 By extrapolation, patients with a modestly elevated platelet count may be at higher risk for developing recurrent coronary thrombus formation compared to patients with lower

Clinical implications

In general, these studies have found statistically significant prognostic value in the complete blood count after accounting for several important clinical covariates in multivariate models such as demographics, medical history, clinical presentation, electrocardiographic characteristics, laboratory data, and treatment interventions, including medications, reperfusion therapy, and revascularization. Nevertheless, only modest clinical interventions can be made at this time. At a minimum,

Conclusion

Although the search for new prognostic markers for ACS is quite active, prognostic information can be obtained from routine hematologic tests. There is strong evidence that elevated WBC counts during ACS are associated with increased risk of mortality, heart failure, shock, and left ventricular dysfunction. Leukocytes may directly mediate adverse outcomes through their biochemical properties or may indirectly measure inflammatory and/or thrombogenic states. Decreased hemoglobin and hematocrit

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