Ola Hammarsten1, Elvar Theodorsson2, Christian Bjurman3, Max Petzold4. 1. Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, The Sahlgrenska Academy at the University of Gothenburg, SE-41345 Gothenburg, Sweden. Electronic address: ola.hammarsten@clinchem.gu.se. 2. Department of Clinical Chemistry and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden. 3. Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, The Sahlgrenska Academy at the University of Gothenburg, SE-41345 Gothenburg, Sweden. 4. Centre for Applied Biostatistics, The Sahlgrenska Academy at the University of Gothenburg, SE-41345 Gothenburg, Sweden.
Abstract
BACKGROUND: Myocardial infarction is more likely if the heart damage biomarker cardiac troponin T (cTnT) is elevated in a blood sample, indicating that cardiac damage has occurred. No method allows the clinician to estimate the risk of myocardial infarction at a specific cTnT level in a given patient. METHODS: Predictive value among lookalikes (PAL) uses pre-test prevalence, sensitivity and specificity at adjacent cTnT limits based on percentiles. PAL is the pre-test prevalence-adjusted probability of disease between two adjacent cTnT limits. If a chest pain patient's cTnT level is between these limits, the risk of myocardial infarction can be estimated. RESULTS: The PAL based on percentiles had an acceptable sampling error when using 100 bootstrapped data of 18 different biomarkers from 38,945 authentic lab measurements. A PAL analysis of an emergency room cohort (n=11,020) revealed that the diagnostic precision of a high-sensitive cTnT assay was similar among chest pain patients at different ages. The higher incidence of false positive results due to non-specific increases in cTnT in the high-age group was counterbalanced by a higher pre-test prevalence of myocardial infarction among older patients, a finding that was missed when using a conventional ROC plot analysis. CONCLUSIONS: The PAL was able to calculate the risk of myocardial infarction at specific cTnT levels and could complement decision limits.
BACKGROUND:Myocardial infarction is more likely if the heart damage biomarker cardiac troponin T (cTnT) is elevated in a blood sample, indicating that cardiac damage has occurred. No method allows the clinician to estimate the risk of myocardial infarction at a specific cTnT level in a given patient. METHODS: Predictive value among lookalikes (PAL) uses pre-test prevalence, sensitivity and specificity at adjacent cTnT limits based on percentiles. PAL is the pre-test prevalence-adjusted probability of disease between two adjacent cTnT limits. If a chest painpatient's cTnT level is between these limits, the risk of myocardial infarction can be estimated. RESULTS: The PAL based on percentiles had an acceptable sampling error when using 100 bootstrapped data of 18 different biomarkers from 38,945 authentic lab measurements. A PAL analysis of an emergency room cohort (n=11,020) revealed that the diagnostic precision of a high-sensitive cTnT assay was similar among chest painpatients at different ages. The higher incidence of false positive results due to non-specific increases in cTnT in the high-age group was counterbalanced by a higher pre-test prevalence of myocardial infarction among older patients, a finding that was missed when using a conventional ROC plot analysis. CONCLUSIONS: The PAL was able to calculate the risk of myocardial infarction at specific cTnT levels and could complement decision limits.