The object of this investigation was to ordeal the hypothesis that ventilation/perfusion V/Q) lung scans in patients with suspected acute pulmonary embolism (PE) can be evaluated upon the basis of the total number of mismatched vascular blemishs irrespective of whether such failings are moderate or large size segmental foibles Lung scan data from the national collaborative close attention of the Prospective investigation of Pulmonary Embolism Diagnosis (PIOPED) were assessed in 383 patients with acute PE and 681 patients in whom suspected PE was exclud The predictive value of the cumulative number of mismatched moderate size segmental flaws (irrespective of the number of mismatched large segmental defects) was nearly the same as that of mismatched large segmental deficiencys (irrespective of the number of mismatched moderate size segmental defects) This recommends that the diagnostic value of mismatched moderate size segmental defaults is the same as mismatched large segmental lacks Lung scans evaluated on the basis of the number of mismatched vascular foibles (moderate and/or large segmental defects) were compared with V/Q scans evaluated in succession the basis of the number of mismatched segmental equivalents.

The object of this investigation was to ordeal the hypothesis that ventilation/perfusion V/Q) lung scans in patients with suspected acute pulmonary embolism (PE) can be evaluated upon the basis of the total number of mismatched vascular blemishs irrespective of whether such failings are moderate or large size segmental foibles Lung scan data from the national collaborative close attention of the Prospective investigation of Pulmonary Embolism Diagnosis (PIOPED) were assessed in 383 patients with acute PE and 681 patients in whom suspected PE was exclud The predictive value of the cumulative number of mismatched moderate size segmental flaws (irrespective of the number of mismatched large segmental defects) was nearly the same as that of mismatched large segmental deficiencys (irrespective of the number of mismatched moderate size segmental defects) This recommends that the diagnostic value of mismatched moderate size segmental defaults is the same as mismatched large segmental lacks Lung scans evaluated on the basis of the number of mismatched vascular foibles (moderate and/or large segmental defects) were compared with V/Q scans evaluated in succession the basis of the number of mismatched segmental equivalents. The maximum likelihood estimates of the areas subject to the receiver operating characteristic (ROC) 1s for the number of mismatched vascular deficiencys and for mismatched segmental equivalents were similar (08512 v 8530) (NS) Stratification according to the nearness or absence of prior cardiopulmonary disease permitted a more accurate assessment of the two clinical groups. Evaluation of V/Q scans according to vascular defects and by segmental equivalents showed similar areas subordinate to the ROC curves. In conclusion, the number of mismatched vascular lacks is as powerful for the assessment of V/Q scans as the number of mismatched segmental equivalents. The number of mismatched vascular defaults however, is easier to interpret and permits a more objective evaluation.

(Chest 1993; 104:1468-72)

PE = pulmonary embolism; PIOPED = Prospective Investigation of Pulmonary Embolism Diagnosis; ROC = receiver operating characteristic; V/Q = ventilation/perfusion

The diagnosis of pulmonary embolism (PE) from ventilation/perfusion (V/Q) lung scans is made onward the basis of the number of mismatched segmental equivalent perfusion defects[1] common segmental equivalent has been defined as individual large segment or two moderate size segments[2] The diagnosis of PE forward the basis of the number of mismatched segmental equivalents assumes that a mismatched moderate size segmental flaw is of less diagnostic value than a mismatched large size segmental defect[2] This assumption has not been largely tested. There is considerable skill and taste required in distinguishing a moderate size mismatched segmental blemish (25 percent to 75 percent of a segment) from a large size mismatched segmental fault (>75 percent of a segment) Experienced readers of radionuclide lung scans oftentimes underestimate the size of segmental defects[3] If it could be shown therefore, that V/Q lung scans could be assessed without the necessity of distinguishing large mismatched segmental blemishs from moderate size mismatched segmental destitutions the interpretation of V/Q scans would be easier and more objective. The end of the present investigation was to standard the hypothesis that the total number of mismatched vascular blemishs irrespective of whether they are large or moderate in size, may have a similar diagnostic power as the number of mismatched segmental equivalents.

Methods

Data from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) were evaluated among 383 patients with acute PE and 681 patients in whom the diagnosis was exclud All patients underwent pulmonary angiography. Patients were in either of sum of two units arms of PIOPED. One assign places to consented to obligatory angiography and the same group underwent angiography at the demand of their attending physicians. These form into groupss and related methods have been described in detail.[1,4]

We previously showed that sensitivity, specificity, and positive predictive value of mismatched segmental equivalent defaults were comparable among patients who concorded to obligatory angiography and those who underwent angiography at the solicit of their physicians.[4] Although there was any bias in the selection of patients in the latter clump we felt that it would be more meaningful to combine the data. All accrues in the present study, therefore, assign to combined data from one as well as the other groups of patients.

A moderate size segmental perfusion failing was defined as 25 percent to 75 percent of a portion and a large segmental flaw was defined as more than 75 percent of a segment[1] A segmental equivalent was defined as common large segment or two moderate size segments[2]

We define a mismatched vascular want as mismatched large or moderate segmental foibles The number of mismatched vascular flaws therefore, was the number of large and/or moderate size mismatched defects

...