Value of structured clinical and scintigraphic protocols in acute pulmonary embolism

PURPOSE: To study the use of a combination of a clinical and scintigraphic protocol in relation to the final outcome diagnosis in patients with clinical suspicion of acute pulmonary embolism (PE). MATERIAL AND METHODS: A total of 170 patients with clinical suspicion of acute PE were all examined with ECG, blood chemistry, chest X-ray, pulmonary scintigraphy and selective pulmonary arteriography. The scintigraphic and clinical probabilities of PE were estimated on visual analogue scales (VASs) by different readers unaware of each others' results. The follow-up time was 6 months. In order to establish the final diagnosis a final outcome committee was created. They analysed in retrospect all the clinical and laboratory data and established whether the patient had had PE or not. RESULTS: The final outcome committee concluded that 53 patients had PE. When the scintigraphic and clinical probability judgements were congruent, a combined probability of 1-25% (i.e low probability) had a negative predictive value of 98%. When the combined probability was 26-75% (i.e. intermediate) half of the cases had PE. With a combined probability of 76-100% (i.e. high) the positive predictive value was 100%. CONCLUSION: By applying a model of combined clinical and scintigraphic probabilities for PE, the diagnosis is ruled in when the combined probability is high, and ruled out when the combined probability is low. However, nearly half of the patients will still have an uncertain diagnosis for which further diagnostic procedures may be allocated.