Coronavirus induced-disease 2019 (COVID-19) was first reported on the 31st of December of 2019 . Since then, it became a pandemic and it brought a heavy burden for the health system of several countries . Symptoms of COVID-19 are non-specific, and its presentation can range from no symptoms to severe acute respiratory syndrome and death . Widespread testing is essential. However, a single negative test does not exclude COVID-19, especially in highly suspected patients  . For a negative test, there are two key factors: pretest probability and test sensitivity. The sensitivity rate of the rRT-PCR is estimated to be 66% - 80%  . Pretest probability depends on several factors, including local COVID-19 prevalence, exposure history and symptoms . Prediction models that combine several of these features to estimate the risk of people being infected could assist medical staff . Efficient diagnosis tools are necessary to help triage patients when allocating limited healthcare resources .
In March 2020, the Portuguese Society of Intensive Care (PSIC) proposed a risk score based on 10 variables to stratify patients with pneumonia regarding Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection probability . It confers a relative score to 10 variables, including demographic, clinical, analytical and imaging data (Table 1). It is considered indicative of a
Table 1. Portuguese Society of Intensive Care (PSIC) risk score for COVID-19.
Abbreviation: CT, Computed tomography; SARS-CoV-2, Severe Acute Respiratory Syndrome-Coronavírus-2; COPD, Chronic Obstructive Pulmonary Disease; LDH, lactate dehydrogenase.
probable COVID-19 case when a patient with lower airway infection has a total punctuation ≥10 . If a patient’s first rRT-PCR test is negative but the score is ≥10, the PSIC recommends considering the patient COVID-19 suspect until a second test (preferably in lower airway samples) is performed 24 to 48 hours later .
In Portugal, this tool was frequently used at admission increasing SARS-CoV-2 infection clinical suspicion. Since few data is available on validated scores predictive of SARS-CoV-2 infection, the aim of this study was to validate the PSIC clinical risk score, applied to inpatients with pneumonia, in predicting a higher probability of COVID-19, based on a single-center department cohort, while assessing the significance of the independent PSIC score variables on the probability of a positive SARS-CoV-2 rRT-PCR test.
This retrospective study was conducted in a COVID-19 dedicated Department, at Centro Hospitalar de Setúbal, E.P.E. (CHS), in a community hospital in Setúbal, Portugal, with the approval of the hospital institutional review board. As only retrospective, non-identifying patient data were collected, informed consent was not applied. Access to clinical file was performed through hospital intranet software namely SClinic.
All patients with pneumonia admitted to the ward between 20/03 and 20/05/2020 were included. Patients without all the required variables to the score calculus were excluded.
Each case of the data set is characterized by 12 independent/predictor variables (including age, gender, comorbidities, symptoms, laboratory and imaging findings as well as exposure as described in the PSIC score), 10 of which are categorical variables with two classes (Yes = 1/No = 0). The dependent variable is a binary variable coded as 0 (Test Negative) and 1 (Test Positive). The independent categorical variables are the 10 score variables proposed by the PSIC codified in binary values considering the presence or absence of male gender, comorbidities (diabetes, COPD, cerebrovascular, oncologic and/or cardiovascular disease such as hypertension or ischemic cardiomyopathy), exposure to a positive SARS-CoV-2 patient, fever and cough at presentation, lymphopenia (<1200/µL), reactive C-protein (CRP) > 5 mg/dL, procalcitonin (PCT) < 0.5 ng/mL, negative respiratory viruses other than SARS-CoV-2 test as well as Legionella pneumophila and Streptococcus pneumoniae urinary antigen tests, lactate dehydrogenase (LDH) > 250 