The clinical diagnosis of pulmonary embolism (PE) remains difficult de
spite years of investigation. The clinical signs and symptoms of pulmo
nary embolism are numerous, but they are not diagnostically accurate.
Radionuclide ventilation perfusion imaging (VQ) has become an importan
t adjunct in screening patients for suspected PE. This study re-evalua
tes the predictive capabilities of various clinical signs and symptoms
in a population of patients in whom angiography was thought to be nec
essary because of clinical concern for PE. One hundred one patients wi
th suspected PE were retrospectively identified. Clinical information
on them was complete, and laboratory studies, VQ imaging, and pulmonar
y angiography were performed. Thirty-seven clinical signs, symptoms, a
nd other characteristics were individually compared for patients whose
angiographic results were positive or negative for PE. Modifying or i
nteractive effects on PE were then examined with logistic regression a
nalysis. Several clinical conditions, including immobilization and rec
ent surgery, were significantly associated with PE. Shortness of breat
h and history of smoking were significantly associated with negative r
esults on pulmonary angiography. A ''high probability'' VQ scan was hi
ghly predictive (P < .0001) of positive results on angiography. When i
nteractive factors for PE were examined, lack of shortness of breath a
nd arterial pH less than or equal to 7.45, lack of shortness of breath
and respiratory rate >23, diaphoresis in a nonsmoker and immobilized
female, were significantly associated with PE. This study again docume
nts the difficulty in using clinical criteria-including signs, symptom
s, and laboratory determinations-to predict PE accurately, even in a p
opulation in which PE was of clinical concern irrespective of the VQ s
can results. The extremely high predictive ability of the VQ scan rein
forces its importance in the evaluation of the patient with suspected
PE.