THE LOW-PROBABILITY LUNG-SCAN - A NEED FOR CHANGE IN NOMENCLATURE

Background: The prognosis in patients with suspected pulmonary embolis m who have a low-probability lung scan has been the focus of much clin ical debate. This is particularly so in patients with underlying cardi ac and pulmonary disease, because these disorders frequently cause low -probability lung scans in the absence of pulmonary embolism. Historic ally, the clinical response has been to exclude pulmonary embolism and withhold treatment on the basis of a low-probability lung scan, which has been regarded as synonymous with a good prognosis. Methods: A pro spective cohort-analytic study to evaluate prognosis, using long-term follow-up, in patients with inadequate cardiorespiratory reserve who h ave presented with suspected pulmonary embolism (inadequate cardioresp iratory reserve, ie, pulmonary edema, right-ventricular failure, hypot ension, syncope, acute tachyarrhythmia, abnormal spirometry [forced ex piratory volume in 1 second, < 1.0, or vital capacity, < 1.5 L], or ab normal arterial blood gases [PO2, < SO mm Hg, or PCO2, > 45 mm Hg]). R esults: The outcomes of the 77 consecutive patients with low-probabili ty lung scans, suspected pulmonary embolism, and inadequate cardioresp iratory reserve were compared with those in 711 consecutive patients w ith good cardiorespiratory reserve and nondiagnostic lung scans who we re entered into the study over the same period of time. Six (7.8%) of the 77 patients died within days of entry with autopsy-proven pulmonar y embolism compared with one (0.14%) of the 711 patients with nondiagn ostic lung scans (P<.0001). Conclusions: Our findings indicate that th e term low-probability lung scan should be abandoned in reference to p atients with inadequate cardiorespiratory reserve, because it is not s ynonymous with a good prognosis and is, indeed, misleading.