Diagnostic yield, clinical probability score and utility of computerized tomographic pulmonary angiography at Moi Teaching and Referral Hospital

Abstract

Background: Pulmonary embolism (PE) is a major cause of cardiovascular mortality in the world ranking third after myocardial infarction and cerebrovascular accidents. Diagnosis of PE is challenging as the symptoms of PE are non-specific. Computed tomographic pulmonary angiography (CTPA) has emerged in recent years as the imaging modality of choice. However, the wide availability of Computed tomography (CT) has led to concerns about the overutilization of CTPA. Use of D dimers and clinical probability scoring tools like the revised Geneva scores are invaluable in stratifying patients according to the probability of PE. However, this has not been explored and no previous studies on clinical probability scores and yield of CTPA exists in our region. Therefore, the study aimed to calculate the diagnostic yield, clinical probability scores and overutilization of CTPA in patients with suspected PE. Objective: To determine the diagnostic yield, clinical probability score, utility and overutilization of CTPA in patients with suspected pulmonary embolism at Moi Teaching and Referral Hospital (MTRH). Methods: This was a cross-sectional study conducted at the MTRH between September 2022 and August 2023. A consecutive sampling technique was applied and recruited 102 adult patients. CTPA were performed using either the 32 slice Siemens and 64 slice Philips CT machines. Demographics, revised Geneva scores and D dimers results were recorded in a questionnaire form. Patients were subsequently categorized into low, intermediate and high probability for PE. CTPA images were uploaded to the Picture Archiving and Communication System (PACS) and interpreted by the principal investigator and 2 radiologists blinded to the clinical probability categories. The diagnostic yield of CTPA was calculated for the low, intermediate and high probability groups and then an overall diagnostic yield for the whole cohort. Data was analyzed using STATA software version 13. Descriptive statistics were summarized as frequencies and percentages, whereas categorical data was analysed using chi square test and fisher’s exact test. A P value of 0.05 was considered statistically significant. Results: The majority of the study participants were female at 62 (60.8%.) and a mean age of 53.2 years. The diagnostic yield was 29.4%. On the Revised Geneva score,7 (6.9%) were low risk,84(82.4%) moderate risk and 11(10.8%) high risk. 0%,25% and 81% in the low intermediate and high risk groups were diagnosed with PE respectively.50(49.0%) of participants had positive conventional D dimers while 52(51.0%) were negative. The revised Geneva score had a sensitivity, specificity, positive predictive value and negative predictive value of 83.3%,44.4%,38.5% and 86.5% respectively. 7 patients (6.9%) had negative D dimers, low risk on the revised Geneva score and no PE on CTPA. Conclusion: The use of D dimers combined with the revised Geneva clinical probability score will stratify patients into risks groups for PE and help to reduce overutilization of CTPA. Recommendation: Stratification of patients using the revised Geneva scores combined with D dimers in low-risk patients should be adopted. Protocols on the diagnostic schema in patients with suspected PE should be developed.