Headache and dizziness occur at carboxyhemoglobin levels of greater than 10%. We studied 89 patients with headache or dizziness for evidence of carbon monoxide exposure. The mean carboxyhemoglobin level was 2.87%. Number of cigarettes smoked per day (r = 0.471; p less than 0.00002), use of gas kitchen stoves for heating purposes (r = 0.252, p less than 0.02), problems with the home heating system (r = 0.278, p less than 0.01), and cohabitants with concurrent headache or dizziness (r = 0.427, p less than 0.01) correlated with carboxyhemoglobin levels. Multiple regression analysis identified number of cigarettes smoked daily, use of stoves for heat, and concurrently symptomatic cohabitants as significant predictors of carboxyhemoglobin level (F = 13.939 [3, 85]; p less than 0.01). Obtaining carboxyhemoglobin levels from patients who used stoves for heat or had similarly affected cohabitants identified 4 of 4 patients with levels greater than 10% (sensitivity, 100%) and excluded 47 of 85 patients with lower levels (specificity, 55.3%). The 4 patients with carboxyhemoglobin levels in excess of 10% may represent occult carbon monoxide poisoning in this population.

We evaluated the AxSYM troponin I (cTnI) immunoassay for assisting in the detection of acute myocardial infarction (AMI). At four sites, the total imprecision (CV) over 20 days was 6.3–10.2%. The minimum detectable concentration was 0.14 ± 0.05 μg/L. Comparison of cTnI measurements between the AxSYM and Stratus (n = 406) over the dynamic range of the AxSYM assay demonstrated good correlation, r = 0.881, with a proportional bias: AxSYM cTnI = 3.50(Stratus cTnI) − 1.10. The confidence intervals (95%) for the slope and intercept were 3.39–3.64 and −1.32 to −0.95, respectively. The expected cTnI concentration in healthy individuals was ≤0.5 μg/L, whereas the ROC curve-determined cutoff for AMI was 2.0 μg/L. This gave a diagnostic sensitivity of 91.8% and specificity of 92.4% when tested in serial samples collected within 24 h of admission in 633 patients presenting with chest pain, of which 122 had an AMI. The concordances of the AxSYM cTnI with the Stratus cTnI, OPUS cTnI, and Access cTnI were 95.3%, 95.1%, and 94.3%, respectively, from patients with suspected AMI. The AxSYM cTnI demonstrated excellent clinical specificity, ≥96%, in skeletal muscle injury, chronic renal disease, and same-day noncardiac surgery patients.

To investigate occult carbon monoxide poisoning in patients with neurologic illness, we prospectively studied 168 patients who presented to the emergency department between December 1987 and February 1988 with neurologic symptoms for evidence of carbon monoxide exposure. Patients with known carbon monoxide poisoning were excluded. The mean carboxyhemoglobin level was 3.1 percent; there were no significant differences in carboxyhemoglobin between categories of neurologic illness (F(5,162) = 1.35; p less than 0.25). Five patients (3 percent) had a carboxyhemoglobin greater than 10 percent, with levels ranging from 11.7 percent to 29.5 percent. After controlling for the effects of active and passive exposure to cigarette smoke, problems with the home heating system (odds ratio 9.6; p less than 0.03) and the presence of cohabitants with concurrent headache or dizziness (odds ratio 21.6; p less than 0.0001) were associated with an increased risk of a carboxyhemoglobin greater than 10 percent. A rule for obtaining carboxyhemoglobin tests only on patients who used gas stoves for heat or who had symptomatic cohabitants would have correctly identified all patients with carboxyhemoglobins greater than 10 percent, correctly excluded 77 percent of patients with lower levels, and eliminated the need for testing in 75 percent of cases. We conclude that unrecognized carbon monoxide poisoning occurs in a small but important fraction of patients with wintertime neurologic illness and can be identified by a characteristic risk factor profile.

No abstract