LEUKOCYTOSIS - A NEW LOOK AT AN OLD MARKER FOR ACUTE MYOCARDIAL-INFARCTION

Objective: To determine the test performance of leukocytosis for ident ifying acute myocardial infarction (AMI) in patients with nondiagnosti c ECGs, admitted to rule out AMI. Methods: A retrospective, comparativ e test performance study was conducted using patients admitted to a un iversity teaching hospital to rule out AMI, Clinical and laboratory in formation was reviewed and hospital laboratory ranges were used to def ine threshold elevations: total creatine kinase (CK), 275 U/L; CK-MB, 7.5 mu g/L; white blood cell (WBC) count, 11.5 x 10(9)/L; and absolute neutrophil count (ANC), 8.0 x 10(9). Sensitivity, specificity, and pr edictive values of the total CK, CK-MB, WBC count, and ANC were calcul ated, and receiver operating characteristic (ROC) curves constructed. Test performances of marker combinations also were determined. Results : The initial WBC count was significantly higher for the subjects who had AMI (11.1 vs 8.8 x 10(9)/L, p < 0.001), For the 688 subjects who h ad nondiagnostic ECGs, sensitivities for the initial total CK, CK-MB, WBC, and ANC were 39%, 73%, 35%, and 36%, respectively, while the corr esponding specificities were 94%, 93%, 85%, acid 86%. Logistic regress ion analysis confirmed leukocytosis as an independent predictor of AMI (adjusted odds ratio 4.08, 95% CI 1.73-9.63), While CK-MB alone was 7 3% sensitive for AMI, the decision rule of either an elevated CK-MB or an elevated WBC count increased this sensitivity to 88% (correspondin g specificity 79%). Similarly, while CK-MB alone was 93% specific for AMI, the combination of an elevated CK-MB and an elevated WBC count in creased this specificity to 99% (corresponding sensitivity 20%). Concl usions: Leukocytosis is significantly associated with AMI, and is a we ak but independent laboratory predictor of this condition, In this pre liminary study of admitted patients suspected of AMI, the combination of the WBC and the CK-MB may have additional diagnostic value over an isolated CK-MB result. Neither parameter in isolation was satisfactori ly sensitive for AMI. Prognostic assessment of the role of the WBC cou nt in clinical decision making should address its complementary role t o that of other clinical and ancillary test parameters.