Table 2.

Multivariable analysis (stepwise Cox proportional hazard model): factors associated with the risk of negativization of nasopharyngeal swab.

Covariates	Category	Adjusted hazard ratio (95% confidence interval)	p-value
Age, years	≤ 70 vs > 70	1.57 (1.11–2.23)	0.011
Days from symptoms to hospital admission	Per 5-days longer	0.76 (0.61–0.94)	0.013
PaO2/FiO2	> 200 vs ≤ 200	1.42 (1.03–1.97)	0.035
Total lymphocytes, per 109/L	> 1 vs ≤ 1	1.55 (1.12–2.15)	0.009

All covariates were measured at baseline. The other tested variables were: gender, body mass index (normal/overweight vs obese), the number of comorbidities* (≥ 1 vs none), use of immunomodulatory drugs (yes vs no), use of antiviral drugs or hydroxychloroquine (yes vs no), use of steroid (yes vs no), lactate dehydrogenase (≤ 330 vs > 330), C-reactive protein (≤ 68.7 vs > 68.7).

*The following comorbidities were considered: malignancies, diabetes, cardiovascular disease, hypertension, asthma, chronic obstructive pulmonary disease.