Interpretation & comparison to existing literature
The overall mean of ultrasound productivity (129 exams per physician-year) in our study is less than indicated in a systematic review, which reported a range of between 131 and 601 exams per GP annually [23]. Many factors have possibly contributed to this difference. Indeed, the number of exams performed by our GPs varied widely, with 49% of the GPs using ultrasound less frequently than weekly. Nevertheless, we were still able to include light users in our data collection. The lower overall productivity compared to the individual years is probably caused by unproductive years with zero exams that are only taken into account in the overall value. In addition, the higher overall number of GPs compared to the individual years is probably caused by GPs that join during the 15-year period but are not visible in the yearly values because of retiring GPs.
Other reasons behind the variation in utilization can potentially be attributed to the allocation of tasks between GPs and specialists, the difference in ultrasound experience among GPs themselves, and the rather low proportion of GPs working full time in Switzerland [24]. These factors may result in the referral of patients to radiologists for ultrasound imaging rather than to other specialized GPs.
The current study provides an important view on the use of ultrasound in relation to patient’s morbidities. Our findings indicate that patients with multi-morbidities receive more ultrasound exams on average, but the study also shows that those with single morbidities have more exams per doctor visit. This finding from billing data is comparable to our survey results and previous studies, which suggest that ultrasound is mainly used for diagnostic purposes and less for therapeutic or treatment evaluation [2, 10]. On the other hand, our findings do not include all morbidities considering that morbidity could only be determined if medications were dispensed to patients during their GP encounters. Therefore, patients who were not dispensed medications, received it outside the GP’s practice, or were prescribed medications not conforming to the PCG model could not be accounted for in the analysis. In addition, our findings are based on the billing data of GPs in contract with the trust center, and do not account for medical encounters outside the billing group. Hence, these factors may have contributed to imprecise estimates in our findings, making it only possible to provide an overview of morbidities among patients receiving ultrasound, rather than establishing relationships between the two. Our study shows that female patients have more ultrasound exams and receive it mainly for the conditions of the abdomen and pelvis. This finding is consistent with previous studies in which females represented 58–60% of patients having ultrasound; chronic abdominal pain was reported as a primary indication for abdominal and pelvic exams [10, 25]. Compared to males, females had more exams for head and neck conditions and procedural guidance. These results are consistent to other studies; the reported indications for such exams included breast lump and pain, neck swelling and enlarged thyroid [25].
Comparable to other studies, our results show that abdominal ultrasound (68%) is the most frequent ultrasound exam performed by GPs in primary care [1, 7, 11, 23, 25–27]. The study also demonstrates that male patients had more ultrasound exams for the abdomen (85.77%) compared to females (56.23%). However, this estimate must be weighed in light of the Tarmed classification system; ultrasound of abdomen includes exams that also investigate genito-urinary system in males, whereas an additional Tarmed category is allocated for genital investigation in females, therefore resulting in this discrepancy. The overall usage of ultrasound in the diagnosis of head and neck, abdominal, and pelvic conditions is equally reflected in billing data of utilization and self-reported indications. However, the use of ultrasound, for indications targeting vessels, musculoskeletal and soft tissues is lower among GPs in the billing data compared to those surveyed. This incomparability in usage between the two groups may suggest underreporting of the utilization of ultrasound by GPs, considering that the billing data only account for examinations that were eligible and submitted for remuneration.
The main clinical conditions indicated by GPs for the use of ultrasound in Swiss primary care correspond to the findings of previous studies [1, 7, 11, 23, 25–27]. Nevertheless, we found variations in the indication of ultrasound for some medical conditions, which may not be in line with recent guidelines and recommendations. For instance, the use of ultrasound for the diagnosis of acute appendicitis is not frequent among our surveyed GPs, although it is recommended in recent studies for suspected acute appendicitis in pediatric and adult patients [28, 29]. Similarly, a meta-analysis conducted in 2011 reported the superiority of ultrasound to radiography in the detection of pneumothorax [30]; however, our survey findings show that only 35% of GPs utilize it for this purpose. Moreover, the application of ultrasound in the diagnosis of fractures or for procedural guidance, particularly in musculoskeletal and soft tissue injections, is relatively low in spite of the diagnostic accuracy and the cost effectiveness of ultrasound imaging in primary care for such indications [31, 32]. It is possible that these conditions are not overly common across Swiss primary care and are more prevalent in emergency room settings, which may therefore explain this disparity.
Contrary to what was previously reported, the current study demonstrates that GPs indeed use ultrasound for gynecological conditions in Swiss primary care, yet at a lower frequency compared to other indications. This finding is equally reflected in the general reduction of the gynecological services provided by primary care physicians in Switzerland [33, 34].
According to our study, the targeted objective of POCUS fits the current clinical practices of GPs; in addition, GPs also use ultrasound for many other and variable conditions including the assessment of liver diseases, splenomegaly, renal colic and obstructive jaundice. Additional applications comprise detection of rib fractures, evaluation of the prostate, palpable neck masses, abscesses and cysts. Nevertheless, the introduction of POCUS certification is expected to shift examinations from the comprehensive evaluation of body organs towards more focused and specific, yet limited clinical questions that are directly related to the complaints of patients.
In line with previous studies, our survey findings emphasize the general view of users that faster diagnosis and earlier treatment are the main reasons for utilizing ultrasound in primary care [2, 7]. Conversely, GPs selected financial benefits among the least important reasons for the utilization. These findings may suggest that the use of ultrasound in primary care is not heavily dependent on the reimbursement, which contradicts other studies that illustrate the financial aspect as a barrier for the use of ultrasound in primary care [11, 19]. Yet, due to the descriptive nature of the survey, we can neither confirm these findings, nor determine to which extent the utilization of ultrasound in primary care is dependent on certification or reimbursement.