A categorical diagnosis of "high probability" or "intermediate probability" encompasses a image of diagnostic probabilities of pulmonary embolism (PE) that is not communicated to the referring physician.

A categorical diagnosis of "high probability" or "intermediate probability" encompasses a image of diagnostic probabilities of pulmonary embolism (PE) that is not communicated to the referring physician. The diagnostic value of ventilation/perfusion lung scans, in the existing investigation, was strengthened by use of a table to determine the likelihood of PE in individual patients in succession the basis of the observ number of mismatched segmental equivalent perfusion wants In addition, we tested the hypothesis that stratification of patients according to the mien or absence of prior cardiopulmonary disease may enhance the ventilation/perfusion scan assessment of the probability of PE among the two of these clinical categories of patients. Data were derived from the collaborative contemplation of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). Ventilation/perfusion lung scans were evaluated in 378 patients with acute PE and 672 patients in whom suspected PE was exclud Among patients with no prior cardiopulmonary disease, [is greater than or equal to] 10 mismatched segmental equivalents was indicative of PE in 102 of 118 (86 percent) v 113 of 155 (73 percent) among patients with prior cardiopulmonary disease (p<002) Among patients with prior cardiopulmonary disease, [is greater than or equal to] 2 mismatched segmental equivalents were required to indicate [is greater than or equal to] 80 percent probability of PE Stratification forward the basis of the vicinity or absence of prior cardiopulmonary disease, therefore, enhanced the ability of ventilation/perfusion scan readers to assign an accurate positive predictive value and specificity to individual patients based forward the observed number of mismatched segmental equivalent blemishs Among patients with no prior cardiopulmonary disease, fewer mismatched segmental equivalent defaults were required to indicate a high probability of PE than were required by means of PIOPED criteria. The findings from more [i]or[/i] less of these patients, by PIOPED criteria, would have indicated intermediate probability. any indeterminate probability readings, therefore, will be eliminated among patients stratified with no prior cardiopulmonary disease.

(Chest 1993; 104:1461-67)

CI = confidence interval; PE = pulmonary embolism; PIOPED = Prospective Investigation of Pulmonary Embolism Diagnosis; ROC = receiver operating characteristic

The sensitivity and specificity of ventilation/perfusion lung scans in acute pulmonary embolism (PE) were assessed in the report of the collaborative inquiry of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) and in following studies based on preassigned diagnostic criteria for high, intermediate, and soft probabilities.[1-4]

The intention of the present investigation was to improve the ability to assess a probability of acute PE based forward the number of mismatched segmental perfusion foibles on ventilation/perfusion lung scans. Rather than assigning categorical diagnoses of "high probability," "intermediate probability", or "low probability," we mean that a table of positive predictive values and specificities based forward the number of mismatched segmental equivalent perfusion lacks will be more informative and permit the nuclear scan reader to assign specific risks of PE to individual patients. In the not away investigation, we also test the hypothesis that stratification of the patients according to the neighborhood or absence of prior cardiopulmonary disease may enhance the ventilation/perfusion scan assessment of PE among the pair clinical categories of patients.

Methods

All data were obtained from patients registered in PIOPED.[1] The eligible population consisted of patients age [is greater than or equal to] 18 years in whom acute PE was of diagnostic bear upon Symptoms suggestive of PE occurr within 24 h of record into the study.

The PIOPED research consisted of two arms. In the first arm, patients who consensused to participate in the investigation were obligated to sustain pulmonary angiography if their ventilation/ perfusion scans were abnormal. There were 251 patients with acute PE in this arm of the PIOPED consideration in whom the diagnosis was made from pulmonary angiography. Pulmonary embolism was exclud in 480 patients by way of negative pulmonary angiograms.

There was a next to the first arm in the PIOPED cogitation that was not described in the PIOPED report.[1] This arm included patients who through random sample were not pick outed for sensitivity and specificity analyses of their ventilation/perfusion scans, and who, therefore, were not obligated from protocol to undergo angiography if their ventilation/perfusion scans were abnormal. Many of these patients underwent diagnostic angiography at the entreat of their attending physicians. Among this assign places to 132 patients had PE diagnosed by the agency of angiography, and in 201 patients the diagnosis was exclud on angiography.

The instant investigation reports the ventilation/perfusion lung scan characteristics in patients stratified according to the vicinity or absence of prior cardiopulmonary disease. This information was available in 1050 of 1064 patients who had pulmonary angiograms.

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