Important Factors in the History, Physical, and Routine Chest Radiograph for Di
July 30, 1999 5 minutes read
Important Factors in the History, Physical, and Routine Chest Radiograph for Diagnosing Pulmonary Embolism
Abstract & Commentary
Synopsis: This paper outlines the accuracy of clinical assessment in the diagnosis of pulmonary embolism. A diagnostic algorithm was derived and validated from a study population with suspected pulmonary embolism prior to lung scanning. The diagnostic algorithm included the identification of three symptoms (singly or in combination): sudden onset of dyspnea, chest pain, and fainting and their association with one or more of the following abnormalities: electrocardiographic signs of right ventricular overload, radiographic signs of oligemia, amputation of the hilar artery, and pulmonary consolidations compatible with infarction. Source: Miniati M, et al. Am J Respir Crit Care Med 1999;159:864-871.Pulmonary embolism (pe) remains a challenging diagnostic problem. Its clinical presentations are known to be deceptive and nonspecific, which makes clinical diagnosis unreliable. A number of studies have been conducted to provide a diagnostic approach in patients suspected of having PE. More often than not, clinical assessment was correct in excluding PE than in identifying PE. Two prospective studies on the diagnosis of PE, PIOPED and PISA-PED, have corroborated the importance of clinical assessment.1,2 The results from these studies suggest that physicians’ estimates of the clinical likelihood of PE, even if based on history and physical, do have predictive value. However, the characteristics of these estimates have not been described, so there is no way of knowing whether others can replicate these estimates.
The study consisted of 750 consecutive patients with suspected PE enrolled in the PISA-PED. Patients were examined independently by six pulmonologists according to a standardized diagnostic protocol prior to lung scanning. Patients who had abnormal scans required pulmonary angiography. Patients were separated into two groups: the first group of 500 patients was used to derive a diagnostic algorithm and the second group of 250 patients was used to validate this algorithm. PE was diagnosed by angiogram in 202 (40%) of the 500 patients in the first group. A diagnostic algorithm that included the identification of the following symptoms (singly or in combination) was developed: sudden onset of dyspnea, chest pain, and fainting and their association with one or more of the following abnormalities: electrocardiographic signs of right ventricular overload, radiographic signs of oligemia, amputation of the hilar artery, and pulmonary consolidations compatible with infarction. The above three symptoms (singly or in combination) were associated with at least one of the above electrocardiographic or radiographic abnormalities in 164 (81%) of 202 patients with confirmed PE and in only 22 (7%) of 298 patients without PE. The rate of correct clinical classification was 88% (440/500).
The accuracy of this clinical diagnostic algorithm was then assessed prospectively in 250 patients referred for lung scanning with clinically suspected PE. PE was diagnosed by pulmonary angiography in 104 of the 188 patients with abnormal scans. The overall prevalence was 42% (104/250), which was comparable with the first group of 500 patients. The above three symptoms (sudden onset of dyspnea, chest pain, or fainting), singly or in combination, were associated with at least one of the four electrocardiographic and radiologic abnormalities specific for PE as described above in 87 (84%) of 104 patients with confirmed PE and in only eight (5%) of the 146 patients without PE. The sensitivity and specificity of the diagnostic algorithm were 84% (95% CI: 77- 91%) and 95% (95% CI: 91-99%), respectively. Thus, the rate of correct clinical classification was 90% (225/250).
On the basis of the above diagnostic algorithm, the clinical probability of PE was calculated as high probability (90%), intermediate probability (50%), or low probability (10%). This clinical estimate of PE was then used as a pretest probability to calculate, after perfusion lung scanning, the post-test probability of PE using Bayes’ theorem.
For a pretest (clinical) probability of PE of 10%, 50%, and 90%, the calculated post-test probability of PE, conditioned by a lung scan result compatible with PE (PE + scan), was 58%, 93%, and 99%, respectively. For a pretest (clinical) probability of 10%, 50%, 90%, the calculated post-test probability of PE conditioned by a lung scan result not compatible with PE (PE—scan) was 2%, 13%, and 58%, respectively. The present study showed that most patients had concordant clinical and perfusion lung scan findings, so that in most patients, PE could be diagnosed or excluded noninvasively by combining well-defined clinical estimates of PE with perfusion lung scan interpretation. However, if the clinical and perfusion lung scan were discordant, further diagnostic testing was required, including pulmonary angiography or other noninvasive procedures (lower extremity duplex scan, D-dimer test, CT angiography).
COMMENT by David Ost, MD
Numerous studies about PE have been performed in order to come up with systematic diagnostic methods. Clinical manifestations have been investigated, but no single sign or symptom is, in itself, diagnostic of PE. Every approach to PE emphasizes the initial clinical suspicion of PE as being critical in the evaluation of PE, but what constitutes a "high" index of suspicion is not well described.
The diagnostic algorithm developed by Miniati and colleagues includes three relevant symptoms (sudden onset of dyspnea, chest pain, and fainting) that were associated with at least one or more of the electrocardiographic and radiographic findings in greater than 80% of patients with confirmed PE. This association occurred in only a few patients in whom the disease had been excluded.
It was a fairly accurate diagnostic algorithm but it failed to identify some 20% of patients with confirmed PE. Miniati et al claimed that in these patients mistakenly classified as not having PE, the severity of the disease was significantly less than those who were correctly diagnosed as having PE.
This study manages to improve the predictive value of the clinical assessment. This diagnostic algorithm may be used as a guideline for clinicians to standardize what constitutes a high index of suspicion. It also highlights for the generalist what factors in the history and physical are most important in evaluating patients with suspected PE. Combining these clinical estimates with the interpretation of V/Q scan should decrease the use of pulmonary angiography. Recent developments in the diagnosis of PE are still being investigated (i.e., CT angiography or MRI) and may be useful in formulating a more specific diagnostic approach for PE, but optimizing the accuracy of the initial index of suspicion will always be important. (Dr. Ost is Assistant Professor of Medicine, NYU School of Medicine, Director of Interventional Pulmonology, Division of Pulmonary and Critical Care Medicine, Northshore University Hospital, Manhasset, NY.)
References
1. PIOPED Investigators. JAMA 1990;263:2753-2759.
2. Miniati M, et al. Am J Respir Crit Care Med 1996; 154:1387-1393.
The clinical assessment of pulmonary embolism, which of the following radiographic abnormalities turn out to be specific for PE?
a. Oligemia
b. Platelike atelectasis
c. Right heart enlargement
d. All of the above.
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