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Survival analysis of time to SARS-CoV-2 PCR negativisation to optimise PCR prescription in health workers: the Henares COVID-19 healthcare workers cohort study
  1. Julio González Martin-Moro1,2,
  2. Marta Chamorro Gómez3,
  3. Galicia Dávila Fernández3,
  4. Ana Elices Apellaniz3,
  5. Ana Fernández Hortelano1,
  6. Elena Guzmán Almagro1,
  7. Angela Herranz Varela4,
  8. Carlos Izquierdo Rodríguez1,
  9. Beatriz Molina Montes5,
  10. Gema Vanesa Sánchez Moreno3,
  11. Alberto Mohedano-Gómez6,
  12. Inés Contreras7,8,
  13. Julio José González López7
  1. 1 Ophthalmology, Henares University Hospital, Coslada, Madrid, Spain
  2. 2 Facultad de Medicina, Universidad Francisco de Vitoria, Pozuelo de Alarcon, Comunidad de Madrid, Spain
  3. 3 Allergy and Immunology, Henares University Hospital, Coslada, Madrid, Spain
  4. 4 Rheumatology, Henares University Hospital, Coslada, Madrid, Spain
  5. 5 ENT, Henares University Hospital, Coslada, Madrid, Spain
  6. 6 ICU, Severo Ochoa University Hospital, Leganés, Madrid, Spain
  7. 7 Ophthalmology, Hospital Ramón y Cajal, Madrid, Madrid, Spain
  8. 8 Ophthalmology, Clínica Rementería, Madrid, Madrid, Spain
  1. Correspondence to Dr Julio González Martin-Moro, Ophthalmology, Henares University Hospital, Coslada 28080, Spain; juliogazpeitia{at}


Objectives Reverse transcriptase PCR (RT-PCR) is considered the gold standard in diagnosing COVID-19. Infected healthcare workers do not go back to work until RT-PCR has demonstrated that the virus is no longer present in the upper respiratory tract. The aim of this study is to determine the most efficient time to perform RT-PCR prior to healthcare workers’ reincorporation.

Materials and methods This is a cohort study of healthcare workers with RT-PCR-confirmed COVID-19. Data were collected using the medical charts of healthcare workers and completed with a telephone interview. Kaplan-Meier curves were used to determine the influence of several variables on the time to RT-PCR negativisation. The impact of the variables on survival was assessed using the Breslow test. A Cox regression model was developed including the associated variables.

Results 159 subjects with a positive RT-PCR out of 374 workers with suspected COVID-19 were included. The median time to negativisation was 25 days from symptom onset (IQR 20–35 days). Presence of IgG, dyspnoea, cough and throat pain were associated with significant longer time to negativisation. Cox logistic regression was used to adjust for confounding variables. Only dyspnoea and cough remained in the model as significant determinants of prolonged negativisation time. Adjusted HRs were 0.68 (0.48–096) for dyspnoea and 0.61 (0.42–0.88) for dry cough.

Conclusions RT-PCR during the first 3 weeks leads to a high percentage of positive results. In the presence of respiratory symptoms, negativisation took nearly 1 week more. Those who developed antibodies needed longer time to negativisate.

  • virology
  • risk assessment
  • investigation of outbreaks of illness
  • immunology
  • hygiene / occupational hygiene

Data availability statement

Data are available upon reasonable request.

This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.

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  • Contributors JGM-M planned, coordinated, participated in data collection, performed statistical analysis of data, and wrote and submitted the manuscript. MCG, GDF, AEA, AFH, EGA, AHV, CIR, BMM and GVSM participated in data collection and study design. AMG and IC participated in study design, and in writing and correcting the manuscript. JJGL participated in the statistical analysis of data and in writing the manuscript.

  • Funding This work has received funding from Fundación para la Investigación e Innovación Biomédica del Hospital Universitario Infanta Sofía y Hospital Universitario del Henares.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.