Clinical characteristics of SARS-CoV-2 pneumonia diagnosed in a primary care practice in Madrid (Spain)

A retrospective observational study was conducted at Federica Montseny PCP at Madrid. This PCP is responsible to attend 21,814 people, 172 patients were included in this study (Fig. 1). The information was obtained from the electronic health record (EHR). The pneumonia cases due to SARS-CoV-2 infection were collected from those patients classified as possible cases who were examined by the PCP from the 10^th of March to the 7^th of Abril of 2020. Patients were eligible for the study if they were over 14 years old and the SARS-CoV-2 pneumonia was diagnosed by their general practitioner ( GP) at PCP. We excluded patients whose diagnosis was made directly at the hospital without PCP intervention and those who did not belong to Federica Montseny PCP.

Patients were encouraged to phone their PCP and stay at home until their GP phoned them on the same day. In mild cases, patients received followed-up appointments at home by remote assessment using daily phone calls. In the case their symptoms worsened, they were advised to come to the PCP for examination where GPs would recommend taking a chest X-ray to rule out pneumonia. The criteria for requiring a chest X-ray were any COVID-19 progression symptom: persistent cough, thoracic pain, dyspnoea, persistent corporal temperature (T > 37.3º) or physical abnormalities (tachypnoea, pulse oximetry ≤ 93%, abnormal lung auscultation). The X-ray department was in the same building than our practice. If pneumonia was diagnosed, the patient was referred to Accident and Emergency department (A&E) for laboratory tests and treatment. Mild pneumonia cases were followed-up by the PCP in conjunction with A&E team. Mild pneumonia was defined mainly as unilateral pneumonia as well as some cases of bilateral pneumonia with local patchy opacities; these patients did not have comorbidities; they were stable with good oximetry and without bad prognosis signs in their laboratory findings. The severe cases were referred straight to the A&E by their GPs. RT-PCR was not accessible at primary care so patients were referred to A&E department at the diagnosis to be tested, some of the patients were admitted in hospitals where we coud not check the RT-PCR result.

The main result was the type of pneumonia: unilateral or bilateral defined by chest X-ray results. Other variables were sociodemographic, comorbidities, prescribed chronic drugs, clinical characteristics of SARS-CoV-2 infection and laboratory results.

Descriptive analyses were carried out for demographic, personal background, physical examination and diagnostic tests, treatment and consequences of SARS-CoV-2 infection. Quantitative variables were expressed as means with standard deviation (SD) or by medians with interquartile range (IRQ), qualitative variables were expressed as percentages. Differences were evaluated using Chi-square test for categorical variables, T-test or ANOVA for normally distributed variables and Wilcoxon-Mann–Whitney or Kruskal–Wallis test for non-normal variables. For all the statistical analyses, p-value (p) < 0.05 was considered significant. Data were stratified by age group (< 50 years, 50–75 years, ≥ 75 years) and pneumonia unilateral or bilateral. All data were anonymised following national and international laws. All analyses were performed using STATA 16 and R 3.4.4.

Fever (144 patients [83.7%]) and cough (140 patients [81.4%]) were the most prevalent symptoms followed by dyspnoea (103 patients [59.9%]) and gastrointestinal disturbances (72 patients [41.9%]). We did not only describe the evolution of the symptoms during the infection till the onset of pneumonia (Fig. 2) but also across the different age groups (Fig. 3); we found myalgia and asthenia also common symptoms in the evolution. A box plot of pneumonia is represented on the bottom of Fig. 2, locating the median diagnosed day in the day 7 of clinical onset and the 50% of the sample from the day 5 to day 10.

We found clinical differences in the pneumonia syndrome among the different ages; not only did ≥ 75 years have 1–3 symptoms (36 patients [86.0%]) more than < 50 years (20 patients [42.0%]) (p < 0.001) but their pneumonia onset was earlier, with a mean day 6.7 (SD 3.7) than the other groups (day 8.1 (SD 4.7) in < 50 years and day 8.3 (SD 3.8) in 50–75 years respectively). The group of < 50 years described ≥ 4 symptoms in 28 patients (58.0%) compared to the other groups (40 patients [49.0%] in 50–75 years and 6 patients [14.0%] in ≥ 75 years) (p < 0.001). The full description of the patients who did not survive can be checked in Additional file 1.

The physical examination was not completed in all the cases; pulse oximetry was recorded in 162 patients (94.1%), heart rate in 138 patients (80.2%), the temperature in 131 patients (76.1%), lung auscultation in 92 patients (53.4%) and respiratory rate in 60 patients (34.8%). Basal pulse oximetry had a median value of 94.0% (IQR 92.0, 96.5), the median temperature was 37.2ºC (IQR 36.7, 37.8). Statistically significant differences in pulse oximetry across the different ages and also the survivors versus no survivors were found. Patients ≥ 75 years had the lowest values (92.0%) compared to < 50 years (96.0%) and 50–75 years (94.0%, p < 0.001) (Table 1). We also found differences comparing non-survivors with survivors (91.0% vs 94.0%) (Additional file 1). The pulse oximetry was ≥ 94% in 98 patients (57.0%) of the whole population, that was achieved by 37 patients (77.0%) of < 50 years group, 48 patients (59.0%) of 50–75 years but only 13 patients (31.0%) of ≥ 75 years group. We did not find differences in the auscultation, respiratory rate or temperature in the different ages.

Unilateral pneumonia was present at 46 patients (26.7% [95% CI 20.3%-33.4%]) of the cases while bilateral pneumonia was found on 126 patients (73.3% [95%CI 66.9%-79.9%]) of the sample. We observed differences between the mean age in patients with unilateral versus bilateral pneumonia (53.7 vs 63.0 years) (Table 2). Patients with bilateral pneumonia had more comorbidities, however we only found statistical significance in hypertension (16 patients [34.8%] in unilateral pneumonia vs 67 patients [53.2%] in bilateral pneumonia, p 0.033), type 2 diabetes (4 patients [8.7%] in unilateral pneumonia vs 29 patients [23.0%] in bilateral pneumonia, p 0.035) or chronic kidney disease (no patients in unilateral pneumonia vs 12 patients [9.5%] in bilateral pneumonia, p 0.030). Patients with unilateral pneumonia presented more frequently myalgia (17 patients [37.0%]) and chest pain (10 patients [21.7%]). Bilateral pneumonia had more dyspnoea (79 patients [62.7%]), but no significant differences were found in clinical characteristics. On the one hand, patients with unilateral pneumonia were prone to normal auscultation compared to bilateral cases (16 patients [34.8%] vs 22 patients [17.5%], p 0.014) and higher pulse oximetry (96% vs 94%, p < 0.001). We found statistical significance between unilateral and bilateral cases in CRP (29.6 vs 81.5 mg/L), lymphocytes (1400.0 vs 1000.0E3/ml) and fibrinogen ≥ 500 mg/dL (24 patients [52.2%] vs 103 [81.7%]). Unilateral pneumonia had more negative RT-PCR, 17 patients (37.0%) vs 19 patients (15.1%) of bilateral ones (p 0.006). 20 patients (43.5%) with unilateral pneumonia required hospital admission in comparison to 120 patients (95.2%) of bilateral pneumonia however pulmonary embolism was only present at bilateral pneumonia (7 patients [5.6%]). Death was present chiefly on bilateral cases (1 patient in unilateral cases [2.2%] vs 10 patients [7.9%], p 0.170) (Table 2).

To our knowledge, our study is the first one to describe patients with SARS-CoV-2 pneumonia diagnosed in a PCP. Besides, we described the clinical differences between bilateral and unilateral cases of pneumonia. However, limitations of this observational study should be addressed. Firstly, this study was carried out in a unique PCP, so the results might not be wildly generalisable. The cardiovascular factors could not be updated in the EHR (especially tobacco or BMI) but the comorbidities are usually updated because we have validated the diagnosis for research with success in other studies [31]. In addition, a bias should be considered because we are located in a primary health centre which include a radiology department, so that we had facilities to diagnose SARS-CoV-2 pneumonia compared to other primary health centers of Madrid. Our study described the symptoms up through the onset of pneumonia but some of unilateral pneumonia should be addressed more thoroughly. On the one hand, we have not collected whether or not they could progress to bilateral pneumonia. On the other hand, we should approach differently those unilateral pneumonia with negative RT-PCR; we should have evidence if the RT-PCR was repeated several times. Further studies should be conducted to clarify these cases. Finally, we based our pneumonia diagnosis in the radiologist description but there could be an interpersonal variability in that description.