Rapid decline of anti-SARS-CoV-2 antibodies in patients on haemodialysis: the COVID-FRIAT study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) patients on haemodialysis (HD) have high mortality. We investigated the value of reverse transcription polymerase chain reaction (RT-PCR) and the dynamic changes of antibodies (enzyme-linked immunosorbent assay immunoglobulin M (IgM) + IgA and/or IgG) in a large HD cohort. METHODS: We conducted a prospective observational study in 10 Madrid HD centres. Infection rate, anti-SARS-CoV-2 antibody dynamics and the incidence of asymptomatic SARS-CoV-2 infection (defined by positive RT-PCR, IgM + IgA and/or IgG) were assessed. RESULTS: From 1 March to 15 April 2020, 136 of 808 (16.8%) HD patients were diagnosed with symptomatic COVID-19 by RT-PCR of nasopharyngeal swabs and 42/136 (31%) died. In the second fortnight of April, RT-PCR and anti-SARS-CoV-2 antibodies were assessed in 763 of the surviving patients. At this point, 69/91 (75.8%) symptomatic COVID-19 patients had anti-SARS-CoV-2 antibodies. Four weeks later, 15.4% (10/65) of initially antibody-positive patients had become negative. Among patients without prior symptomatic COVID-19, 9/672 (1.3%) were RT-PCR positive and 101/672 patients (15.0%) were antibody positive. Four weeks later, 62/86 (72.1%) of initially antibody-positive patients had become negative. Considering only IgG titres, serology remained positive after 4 weeks in 90% (54/60) of patients with symptomatic COVID-19 and in 52.5% (21/40) of asymptomatic patients. The probability of an adequate serologic response (defined as the development of anti-SARS-CoV-2 antibodies that persisted at 4 weeks) was higher in patients who had symptomatic COVID-19 than in asymptomatic SARS-CoV-2 infection {odds ratio [OR) 4.04 [95% confidence interval (CI) 2.04-7.99]} corrected for age, Charlson comorbidity index score and time on HD. Living in a nursing home [OR 5.9 (95% CI 2.3-15.1)] was the main risk factor for SARS-CoV-2 infection. CONCLUSIONS: The anti-SARS-CoV-2 antibody immune response in HD patients depends on clinical presentation. The antibody titres decay earlier than previously reported for the general population. This inadequate immune response raises questions about the efficacy of future vaccines.

Serology in the xxi century: is it still of interest? / Serología en el siglo xxi: ¿continúa teniendo interés?

Serological techniques have developed in recent years, and are now more sensitive, automated and easier to interpret. However, serology in often being replaced by direct diagnosis based on molecular biology, essentially PCR (polymerase chain reaction) techniques. Nevertheless, in some cases, serology continues to be an essential feature in the routine work of microbiology laboratories, such as in screening pregnant wo-men, studies of transplant donors and recipients, diagnosis of certain viruses and bacteria, and epidemiological and prevalence studies. The improved speed, sensitivity and specificity of direct diagnostic methods will probably continue to decrease antibody-based diagnosis. Thus, serology will not be relevant in the management of acute patient infections; however, it will continue to be relevant in population-based studies and in certain syndromic studies, with more automated and more sensitive, specific and cheap methods. Supplement information: This article is part of a supplement entitled «SEIMC External Quality Control Programme. Year 2016¼, which is sponsored by Roche, Vircell Microbiologists, Abbott Molecular and Francisco Soria Melguizo, S.A. © 2019 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosasy Microbiología Clínica. All rights reserved.

[Molecular diagnosis of parasitic and fungal infections]. / El diagnóstico molecular en las infecciones parasitarias y fúngicas.

Conventional microbiological diagnosis of fungal infections and parasitic diseases has been characterized by low diagnostic sensitivity, laboriousness, and the need for expert microscopists. Consequently, diagnostic methods based on the detection of nucleic acids are a magnificent alternative to overcome these problems, but have not yet provided a satisfactory response in all situations. The molecular methods used are varied and most are based on techniques of nucleic acid amplification. These techniques have proved useful for mycological and parasitological diagnosis, for epidemiological and taxonomic studies, and for monitoring the response to different treatments and detection of resistance. The introduction of these techniques in developing countries may be hampered by their higher cost but molecular diagnostic methods are already beginning to spread in clinical microbiology laboratories and are competing successfully with traditional methods. The present article reviews the current status of molecular methods in the diagnosis of fungal and parasitic infections.