The correlation between point-of-care ultrasound and digital tomosynthesis when used with suspected COVID-19 pneumonia patients in primary care.

Background: The use of lung ultrasound (LU) with COVID-19 pneumonia patients should be validated in the field of primary care (PC). Our study aims to evaluate the correlation between LU and radiographic imaging in PC patients with suspected COVID-19 pneumonia.

Methods: This observational, prospective and multicentre study was carried out with patients from a PC health area whose tests for COVID-19 and suspected pneumonia had been positive and who then underwent LU and a digital tomosynthesis (DT). Four PC physicians obtained data regarding the patients' symptoms, examination, medical history and ultrasound data for 12 lung fields: the total amount of B lines (zero to four per field), the irregularity of the pleural line, subpleural consolidation, lung consolidation and pleural effusion. These data were subsequently correlated with the presence of pneumonia by means of DT, the need for hospital admission and a consultation in the hospital emergency department in the following 15 days.

Results: The study was carried out between November 2020 and January 2021 with 70 patients (40 of whom had pneumonia, confirmed by means of DT). Those with pneumonia were older, had a higher proportion of arterial hypertension and lower oxygen saturation (sO₂). The number of B lines was higher in patients with pneumonia (16.53 vs. 4.3, p < 0.001). The area under the curve for LU was 0.87 (95% CI 0.78-0.96, p < 0.001), and when establishing a cut-off point of six B lines or more, the sensitivity was 0.875 (95% CI 0.77-0.98, p < 0.05), the specificity was 0.833 (95% CI 0.692-0.975, p < 0.05), the positive-likelihood ratio was 5.25 (95% CI 2.34-11.79, p < 0.05) and the negative-likelihood ratio was 0.15 (95% CI 0.07-0.34, p < 0.05). An age of ≥ 55 and a higher number of B lines were associated with admission. Patients who required admission (n = 7) met at least one of the following criteria: ≥ 55 years of age, sO₂ ≤ 95%, presence of at least one subpleural consolidation or ≥ 21 B lines.

Conclusions: LU has great sensitivity and specificity for the diagnosis of COVID-19 pneumonia in PC. Clinical ultrasound findings, along with age and saturation, could, therefore, improve decision-making in this field.