Missed myocardial infarctions in ED patients prospectively categorized as low risk by established risk scores.

STUDY OBJECTIVES: Few studies have prospectively compared multiple cardiac risk prediction scores. We compared the rate of missed acute myocardial infarction (AMI) in chest pain patients prospectively categorized as low risk by unstructured clinical impression, and by HEART, TIMI, GRACE, and EDACS scores, in combination with two negative contemporary cardiac troponins (cTn) available in the U.S. METHODS: We enrolled 434 patients with chest pain presenting to one of seven emergency departments (ED). Risk scores were prospectively calculated and included the first two cTn. Low risk was defined for each score as HEART≤3, TIMI≤0, GRACE≤50, and EDACS≤15. AMI incidence was calculated for low risk patients and compared across scores using Χ2 tests and C statistics. RESULTS: The patients' median age was 57, 58% were male, 60% white, and 80 (18%) had AMI. The missed AMI rate in low risk patients for each of the scores when combined with 2 cTn were HEART 3.6%, TIMI 0%, GRACE 6.3%, EDACS 0.9%, and unstructured clinical impression 0%. The C-statistic was greatest for the EDACS score, 0.94 (95% CI, 0.92-0.97). CONCLUSIONS: Using their recommended cutpoints and non high sensitivity cTn, TIMI and unstructured clinical impression were the only scores with no missed cases of AMI. Using lower cutpoints (GRACE≤48, TIMI=0, EDACS≤11, HEART≤2) missed no case of AMI, but classified less patients as low-risk.

Comparison of BD Vacutainer® Rapid Serum Tube and plasma for haemolysis markers in the emergency department.

BACKGROUND: In recent years, a rapid-clotting serum tube, BD Vacutainer® Rapid Serum Tube (RST™), was introduced to improve turn-around times for serum samples. Previous studies reported reduced concentrations of some markers of haemolysis in RST specimens compared to other serum or plasma samples. We aimed to compare RST to plasma tubes for haemolysis markers in an emergency department (ED) setting, where increased rates of haemolysis are commonly seen. METHODS: Patients presenting to ED over an eight-day period had an RST, BD Vacutainer® PST™ II (plasma) Tube and BD Vacutainer® Heparin (non-gel, plasma) Tube collected. Blood was drawn from an intravenous cannula, and samples were promptly analysed for haemolysis index, potassium, phosphate, aspartate aminotrasferase (AST), magnesium and lactate dehydrogenase (LD). RESULTS: A total of 347 patient samples were included, and 9.2% of the PST samples were haemolysed. The RST tubes had small increases in all of the haemolysis markers compared to both plasma tubes (P ≤ 0.005), except LD which was lower in the RST group. There were no significant differences in the proportion of results above the upper reference limit between the tubes, except for LD which had a lower proportion in RST samples (P ≤ 0.002). CONCLUSION: Compared to plasma, RST specimens show small increases in several haemolysis markers, consistent with known differences between serum and plasma, but the proportion of elevated haemolysis markers is similar to plasma. In a setting with a high haemolysis rate such as ED, RST specimens provide a non-inferior sample type for markers of haemolysis.