Carboxyhemoglobin levels in patients with flu-like symptoms

Subacute carbon monoxide poisoning is commonly misdiagnosed as an influenza-like viral illness. All patients presenting to the triage nurse at University Hospital with flu-like symptoms during February 1985 were asked to give blood samples for carboxyhemoglobin determination. Fifty-five patients (10% of those eligible) with headache, dizziness, nausea, vomiting, diarrhea, weakness, general malaise, or shortness of breath were enrolled in the study. Carboxyhemoglobin levels ranged from 0 to 21%. Thirteen patients (23.6%) of this self-selected subgroup had carboxyhemoglobin levels ⩾ 10%. There was no statistically significant difference in carboxyhemoglobin levels between smokers and nonsmokers. More patients using wood heat had elevated carboxyhemoglobin levels than patients using any other form of heating (P < .05). No patient with a carboxyhemoglobin level ⩾ 10% was diagnosed as having subacute CO poisoning by emergency physicians. Physicians must seek out the possibility of CO toxicity in patients with flu-like illness, particularly in inner-city populations during the heating months. Fundoscopy and COHb levels may be useful in selected cases to correctly diagnose patients and avoid a return to a hazardous environment with potentially fatal consequences.