Establishment of reference intervals for complete blood count in times of COVID-19 and vaccination.

"Potential conflict of interest: None declared."

"A descriptive cross-sectional study was conducted on donors who attended the blood bank service of HTVFN (in process of accreditation by Joint Commission International) in Mexico City from June to September 2021. The Mexican Official Standard (NOM) 007-SSA3-2011 states that all laboratory reports must include the RI of each analyte by sex and age group (). Donor candidates were previously instructed to present with a minimum of 8 hours of fasting and a rest of at least 8 hours, previous low-fat diet, no strenuous exercise. During venous blood sampling on the forearm (duration time approximately 4 minute), donation candidates remained seated. We included men and women who were accepted as donors in accordance with the guidelines of the NOM 253-SSA1-2012, which establishes the requirements for the provision of human blood and its components for therapeutic purposes: their age ranged from 18 to 65 years, no alcohol, caffeine or tobacco use, non-pregnant and non-breastfeeding women, no oral contraceptive and/or aspirin treatment, who weighed more than 50 kg and who were considered healthy by questionnaire and medical examination, and who, if they had a COVID-19 background, their donation was postponed by 14 days after the disappearance of symptoms (, ). Only donors who had been vaccinated with attenuated virus vaccines, whole attenuated or inactivated virus vaccines or if they did not know the type of vaccine administered, should defer their donation for 14 days and individuals who had received mRNA vaccines, non-replicating viral vector, or protein subunit vaccines, did not need to defer donation (). Donors who decided not to participate in this study at the end of their donation process, who had lipaemic and/or haemolysed samples, who presented obesity and donors with surnames that were not of Spanish origin and with less than three generations living in the country were excluded. All donors who agreed to participate signed an informed consent. The present study was approved by the ethics and research committee of the HTVFN (institutional registration number R-2021-3401005)."