Diagnosing pulmonary embolism: a question of too much choice?

Study of compliance with a clinical pathway for suspected pulmonary embolism

BACKGROUND/AIMS

Clinical pathways to guide the investigation of suspected pulmonary embolism have been increasingly adopted by emergency departments worldwide. This study evaluated the compliance with a clinical pathway that combines risk assessment (Wells score) with d-dimer, ventilation-perfusion scanning or computed tomographic pulmonary angiography (CTPA). The aims of this study were to identify factors that contribute to compliance and to assess patient outcomes and resource utilization.

METHODS

Repeated retrospective chart reviews of 239 patients who underwent investigation for pulmonary embolism through our emergency department extracted patient demographics, pathway parameters and patient outcomes. A phone interview at 3-month follow up was carried out.

RESULTS

Incidence of pulmonary embolism was 8.4% (n= 20). Compliance to the clinical pathway occurred in 120 subjects (50.2%). Non-compliance occurred in 71 subjects (29.7%). Forty-eight subjects (20.1%) underwent risk assessments, but subsequent diagnostic tests did not conform to the stated pathway (partial compliance). Compliance was poor in subjects assessed by non-emergency department doctors (χ(2) = 27.95, P≤ 0.001). Compliance occurred less in pregnant subjects (χ(2) = 7.27, P= 0.007) and those with chronic respiratory disease (χ(2) = 5.31, P= 0.021). Subjects in the compliant group were less likely to undergo CTPA (odds ratio 2.07 (1.16-3.70), P= 0.012).

CONCLUSIONS

Compliance with this clinical pathway allowed emergency department doctors in an Australian university teaching hospital to complete diagnostic testing for suspected pulmonary embolism appropriately unless non-emergency department doctors became involved. Compliance with this pathway altered the distribution of diagnostic tests performed with less reliance on CTPA, but was not associated with better patient outcomes.

Likelihood ratios increase diagnostic certainty in pulmonary embolism

Pulmonary embolism (PE) is a difficult diagnosis to confirm. The choice of tests has led to a myriad of algorithms. Diagnostic uncertainty can be quantified by the application of the tests' likelihood ratios (LR). Positive and negative LR enable the conversion of a pretest to a post-test probability, given a positive and negative test result, respectively. Thus, a pretest probability of <17% and a negative D-dimer with a negative LR of 0.05 (sensitivity 98%, specificity 40%) lead to a post-test probability of PE of <1%. Ventilation perfusion (V/Q) scans with a normal, very low, low, intermediate and high probability result have an LR of 0, 0.125, 0.25, 1 and 17, respectively. Also, patients with a V/Q scan result other than normal or high probability still have a post-test probability of PE from 3 to 65%. Positive and negative computed tomography pulmonary angiograms (CTPA) have an LR of 8.6 and 0.06, respectively (sensitivity 95%, specificity 89%). Patients with a high pretest probability and negative CTPA again still have a post-test probability of more than 10%. However, as the post-test probability after one test becomes the pretest probability for the next, test results used cumulatively progressively narrow the gap to a final diagnosis. The post-test probability after a D-dimer, V/Q scan, CTPA, leg ultrasound or pulmonary angiography, alone or in any combination or in any order, can be calculated using their LR. Use of LR thus assists in the precise interpretation of test results, such as in complex algorithms for PE.

Two cases of pulmonary embolism after head and neck surgery

Pulmonary embolism (PE) is a prominent cause of morbidity and mortality in surgical patients. Here, we report two cases of PE following head and neck surgery: (1) in case 1, the patient underwent endoscopic sinus surgery (ESS), and (2) in case 2, the patient was suspected PE after resection of the parotid gland and radical neck dissection. Prophylactic compression devices were used during the operation in both cases. In case 1, PE was diagnosed 3 days following surgery after the patient complained of dyspnea while walking. PE was successfully treated by intravenous administration of heparin. In case 2, PE was strongly suspected 13 days following surgery after the patient experienced syncope and chest pain and exhibited abnormal findings on a cardiac echogram. This patient died 18 h after the onset of cardiac symptoms. Despite prophylactic measures taken during surgery, the prognosis was poor for this patient due to numerous high-risk factors (e.g., advanced age, obesity, prolonged immobilization). Although the incidence of postoperative PE in our department during the last 7 years is very low (0.04%), the frequency of postoperative PE in Japan has steadily increased in recent years. PE still is one of the most significant complications leading to morbidity and mortality following surgery. Given the gaining prominence of PE, we conclude that otolaryngologists including those in Japan should be reminded of high-risk factors associated with PE and be made aware of prophylactic treatments newly aimed at reducing the frequency of PE.