Table 1

Classification and characteristics of study variables

VariableConceptual definitionOperational definitionType
AgeDate at recruitment minus date of birthYears of ageQuantitative
GenderMale or female genotype of the personMale/femaleQualitative nominal
WeightHow much the patient weighs at the time of study inclusionWeight, kilogramsContinuous quantitative
SizeHow tall is the patient from head to toe at the time of study inclusionHeight, centimetresContinuous quantitative
Body mass indexThe division between weight by height squared at the time of inclusion in the studyUnits of kg/cm2Continuous quantitative
OccupationRemunerative work performed by the participant at the time of recruitmentUnemployed, informal, unskilled employee, microentrepreneur or saleswoman, administrative employee, professional and entrepreneurQualitative nominal
Civil statusCivil status of the individualMarried, single, widowed, divorced and common-law unionQualitative nominal
Level of studyYears completed and approved at the time of study recruitmentNo studies, primary, secondary, preparatory, technical career, undergraduate and postgraduateOrdinal qualitative
Alcohol intakeConsumption of alcoholic beveragesIntake of alcoholic beveragesQualitative nominal
Smoking habitHabitual tobacco uses at the time of recruitmentNumber of packs of cigarettes consumed per dayQuantitative
Drug’s useRegular use of chemicals such as amphetamines, cocaine, marijuana, LSD, heroin and glassConsumption of drugsQualitative nominal
HypertensionElevation of blood pressure >130/80Positive/negativeQualitative nominal
AsthmaChronic inflammatory disease characterised by bronchial hyperactivity with recurrent episodes of bronchospasmPositive/negativeQualitative nominal
DiabetesGroup of metabolic diseases, which occurs when the pancreas does not produce enough insulin or when the body does not use the insulin it produces effectivelyPositive/negativeQualitative nominal
ObesityPathological state characterised by a general excess or excessive accumulation of fat in the bodyPositive/negativeQualitative nominal
SARS-CoV-2 pneumoniaA form of severe pneumonia caused by coronavirusPositive/negativeQualitative nominal
DeathStatistical term that describes the death of an individualPositive/negativeQualitative nominal
Intensive care unitSpecial facility in a hospital area, which provides life support to critically ill patients, requiring intensive supervision and monitoringPositive/negativeQualitative nominal
Severe pneumoniaDefined by the American Thoracic Society Criteria requiring at least one main criterion (need for invasive mechanical ventilation and shock with need for vasopressors), or three minor criteria (respiratory rate >30 bpm, PaO2/FiO2 ratio <250, infiltrates multilobars, confusion/disorientation, uremia (>20 mg/dL), leucopenia (<4000), thrombocytopaenia (<100 000 platelets/mm3), hypothermia (core temperature <36°C) or hypotension requiring aggressive fluid resuscitationPositive/negativeQualitative nominal
PneumoniaAcute infection of the lung parenchyma, accompanied by bilateral infiltrates on chest X-rayPositive/negativeQualitative nominal
ConfusionGlasgow scale less than 15Positive/negativeQualitative nominal
HypothermiaBody temperature less than 36°CPositive/negativeQualitative nominal
ThrombocytopaeniaTotal platelets less than 100 000 per mm3Positive/negativeQualitative nominal
Arterial hypotensionSystolic blood pressure less than 90 mm Hg or mean arterial pressure less than 60 mm HgPositive/negativeQualitative nominal
SepsisRapid SOFA score (qSOFA) with two of the following three clinical variables: Glasgow ≤13, systolic pressure ≤100 mm Hg or respiratory rate ≥22 bpmPositive/negativeQualitative nominal
qRT-PCR for SARS-CoV-2Molecular diagnosis for SARS-CoV-2 from viral RNAPositive/negativeQualitative nominal
Septic shockArterial hypotension that persists after resuscitation volume and that requires vasopressors to maintain MAP (mean arterial pressure) ≥65 mm Hg and lactate ≥2 mmol/L (18 mg/dL) in the absence of hypovolaemiaPositive/negativeQualitative nominal
Adverse events related to the use of hydroxychloroquineIndirect drug-related mortality, nausea, vomiting, abdominal pain, rash, itchy skin, hair loss, QT segment elongation on ECG, corneal opacity, cardiac arrhythmias and heart failurePositive/negativeQualitative nominal
Adverse events related to the use of bromhexineIndirect drug-related mortality, nausea, vomiting, abdominal pain, rash and diarrhoeaPositive/negativeQualitative nominal