Comparison of two immunoassays for detection of anti-SARS cov-2 antibodies among healthcare workers at a tertiary referral Hospital in Nairobi, Kenya

Background: Tests for antibodies against severe acute respiratory syndrome coronavirus 2, the aetiologic agent of coronavirus disease 2019, provide evidence of past infection or immunization. At the individual level, they are useful as markers of protection against severe disease and in cases where the diagnosis by nucleic acid amplification is inconclusive. At the population level, they are an indirect measure of exposure and may be useful in monitoring changes in viral infection or uptake of immunization over time. The interpretation and optimal use of antibody assays on populations requires an appreciation of the wide variability in individual antibody responses, the timing of testing, and individual assay performance. Direct comparison of assays in representative populations is one way of providing information that will aid in optimization of their use. Objectives: The primary objective in this pre-vaccine study was to determine the difference in estimates of prevalence of anti-SARS-CoV-2 antibodies in a population of health care workers tested using two qualitative immunoassay platforms targeting two different SARS-CoV-2 proteins. Secondary objectives were: (i) to determine the proportion of discordant results, (ii) to investigate sex, age, and time since exposure as predictors of discordance, and (iii) describe the changes in antibody level with time for each assay. Methods: This was a secondary analysis of data collected from an earlier cross-sectional study that determined seroprevalence of antibodies against nucleocapsid and spike proteins of SARSCoV-2 in sera collected from the study population. Antibodies against SARS-CoV-2 were detected using two different assays detecting anti-nucleocapsid and anti-spike antibodies in samples collected at a single time point for each participant. The proportion with a positive result by each assay was determined, as was the proportion of discordant results. Age, sex, and time as predictors of discordance were explored using a binomial logistic regression model. Plots of antibody index against time were prepared for each assay. Results:A total of 1477 serum samples from 643 (43.5%) males and 834 females were analysed. This study found a prevalence of 18.3% (95% CI, 16.4% – 20.3%) and 26.5% (95% CI, 24.2% – 28.7%), respectively, of antibodies against nucleocapsid and spike. Overall, 162 (10.9%) participants had discordant antibody results. Of the 107 individuals with a prior PCR positive result, discordance was found in 27 (25.2%). Discordance was found to increase with v time since positive PCR; 100% of results of samples collected at 28 weeks post PCR were discordant. One hundred forty-one (87.1%) of participants with discordant results had a positive spike result and negative nucleocapsid result; this figure was 74.1% in those with a prior positive PCR result. Age (OR = 0.94, 95% CI 0.89 – 1.00, P Conclusion: Following natural infection by SARS-CoV-2, the seroprevalence of anti-spike antibodies is higher than that of anti-nucleocapsid antibodies in a population naïve to the SARS CoV-2 vaccine. Discordance in antibody result is more likely the longer the interval between exposure and testing. Antibodies against spike remain detectable for a longer duration than those against nucleocapsid. Assays detecting anti-spike antibodies would result in higher estimates of seroprevalence in surveillance studies

Neonatal reference intervals for thyroid stimulating hormone and free thyroxine assayed on a Siemens Atellica® IM analyzer: a cross sectional study

Background Deriving population specific reference intervals (RIs) or at the very least verifying any RI before adoption is good laboratory practice. Siemens has provided RIs for thyroid stimulating hormone (TSH) and free thyroxine (FT4) determined on their Atellica® IM analyzer for all age groups except the neonatal age group which provides a challenge for laboratories that intend to use it to screen for congenital hypothyroidism (CH) and other thyroid disorders in neonates. We set out to determine RIs for TSH and FT4 using data obtained from neonates undergoing routine screening for CH at the Aga Khan University Hospital, Nairobi, Kenya. Methodology TSH and FT4 data for neonates aged 30 days and below were extracted from the hospital management information system for the period March 2020 to June 2021. A single episode of testing for the same neonate was included provided both TSH and FT4 were done on the same sample. RI determination was performed using a non-parametric approach. Results A total of 1243 testing episodes from 1218 neonates had both TSH and FT4 results. A single set of test results from each neonate was used to derive RIs. Both TSH and FT4 declined with increase in age with a more marked decline seen in the first 7 days of life. There was a positive correlation between logFT4 and logTSH (rs (1216) = 0.189, p = \u3c 0.001). We derived TSH RIs for the age groups 2–4 days (0.403–7.942 μIU/mL) and 5–7 days (0.418–6.319 μIU/ mL), and sex specific RIs for males (0.609–7.557 μIU/mL) and females (0.420–6.189 μIU/mL) aged 8–30 days. For FT4, separate RIs were derived for the age groups 2–4 days (1.19–2.59 ng/dL), 5–7 days (1.21–2.29 ng/dL) and 8–30 days (1.02–2.01 ng/dL). Conclusion Our neonatal RIs for TSH and FT4 are different from those published or recommended by Siemens. The RIs will serve as a guide for the interpretation of thyroid function tests in neonates from sub-Saharan Africa where routine screening for congenital hypothyroidism using serum samples is done on the Siemens Atellica® IM analyzer

Post-vaccination SARS-CoV-2 IgG spike antibody responses among clinical and non-clinical healthcare workers at a tertiary facility in Kenya

Introduction: Following the coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, vaccination became the main strategy against disease severity and even death. Healthcare workers were considered high-risk for infection and, thus, were prioritised for vaccination. Methods: A follow-up to a SARS-CoV-2 seroprevalence study among clinical and non-clinical HCWs at the Aga Khan University Hospital, Nairobi, we assessed how vaccination influenced SARS-CoV-2 anti-spike IgG antibody responses and kinetics. Blood samples were drawn at two points spanning 6 to 18 months post-vaccination, and SARS-CoV-2 spike antibody levels were determined by enzyme-linked immunosorbent assay. Results: Almost all participants, 98% (961/981), received a second vaccine dose, and only 8.5% (83/981) received a third dose. SARS-CoV-2 spike IgG antibodies were detected in 100% (961/961) and 92.7% (707/762) of participants who received two vaccine doses, with the first and second post-vaccine test, respectively, and in 100% (83/83) and 91.4% (64/70) of those who received three vaccine doses at the first and second post-vaccine test, respectively. Seventy-six participants developed mild infections, not requiring hospitalisation even after receiving primary vaccination. Receiving three vaccine doses influenced the anti-spike S/Co at both the first (p\u3c0.001) and second post-vaccination testing (p\u3c0.001). Of those who tested SARS-CoV-2 positive, the anti-spike S/Co ratio was significantly higher than those who were seronegative at the first post-vaccine test (p = 0.001). Side effects were reported by almost half of those who received the first dose, 47.3% (464/981), 28.9% (278/961) and 25.3% (21/83) of those who received the second and third vaccine doses, respectively. Conclusion: Following the second dose of primary vaccination, all participants had detectable anti-spike antibodies. The observed mild breakthrough infections may have been due to emerging SARS-CoV-2 variants. Findings suggest that although protective antibodies are induced, vaccination protected against COVID-19 disease severity and not necessarily infection

Seroprevalence, correlates and kinetics of SARS-CoV-2 nucleocapsid IgG antibody in healthcare workers and nonclinical staff at a tertiary hospital: a prevaccine census study

Background Healthcare workers and nonclinical staff in medical facilities are perceived to be a high-risk group for acquiring SAR-CoV-2 infection, and more so in countries where COVID-19 vaccination uptake is low. Serosurveillance may best determine the true extent of SARS-CoV-2 infection since most infected HCWs and other staff may be asymptomatic or present with only mild symptoms. Over time, determining the true extent of SARS-CoV-2 infection could inform hospital management and staff whether the preventive measures instituted are effective and valuable in developing targeted solutions. Methods This was a census survey study conducted at the Aga Khan University Hospital, Nairobi, between November 2020 and February 2021 before the implementation of the COVID-19 vaccination. The SARS-CoV-2 nucleocapsid IgG test was performed using a chemiluminescent assay. Results One thousand six hundred thirty-one (1631) staff enrolled, totalling 60% of the workforce. The overall crude seroprevalence was 18.4% and the adjusted value (for assay sensitivity of 86%) was 21.4% (95% CI; 19.2–23.7). The staff categories with higher prevalence included pharmacy (25.6%), outreach (24%), hospital- based nursing (22.2%) and catering staff (22.6%). Independent predictors of a positive IgG result after adjusting for age, sex and comorbidities included prior COVID-19 like symptoms, odds ratio (OR) 2.0 [95% confidence interval (CI) 1.3–3.0, p = 0.001], a prior positive SARS-CoV-2 PCR result OR 12.0 (CI: 7.7–18.7, p<0.001) and working in a clinical COVID-19 designated area, OR 1.9 (CI 1.1–3.3, p = 0.021). The odds of testing positive for IgG after a positive PCR test were lowest if the antibody test was performed more than 2 months later; OR 0.7 (CI: 0.48–0.95, p = 0.025). Conclusions The prevalence of anti- SARS-CoV-2 nucleocapsid IgG among HCWs and nonclinical staff was lower than in the general population. Staff working in clinical areas were not at increased risk when compared to staff working in non-clinical areas

Serum ferritin and its association with haemoglobin levels and body mass index in an urban adult population in Kenya

No abstract availabl

Seroprevalence, correlates and kinetics of SARS-CoV-2 Nucleocapsid IgG antibody in healthcare workers at a tertiary hospital: a prevaccine census study

Background: Healthcare workers are perceived to be a high-risk group for acquiring SAR-CoV-2 infection, and more so in countries where COVID-19 vaccination uptake is low. Serosurveillance may best determine the true extent of SARS-CoV-2 infection since most infected HCWs may be asymptomatic or present with only mild symptoms. Over time, determining the true extent of SARS-CoV-2 infection could inform hospital management and staff whether the preventive measures instituted are effective and valuable in developing targeted solutions. Methods: This was a census survey study conducted at the Aga Khan University Hospital, Nairobi, between November 2020 and February 2021 before the implementation of the COVID-19 vaccination. The SARS-CoV-2 nucleocapsid IgG test was performed using a chemiluminescent assay. Results:One thousand six hundred thirty-one (1631) staff enrolled, totalling 60% of the workforce. The overall crude seroprevalence was 18.4% and the adjusted value (for assay sensitivity of 86%) was 21.4% (95% CI; 19.2-23.7). The HCW groups with higher prevalence included pharmacy (25.6%), outreach (24%), hospital-based nursing (22.2%) and catering staff (22.6%). Independent predictors of a positive IgG result included prior COVID-19 like symptoms, odds ratio (OR) 1.9 [95% confidence interval (CI) 1.3-2.9, p=0.002], and a prior positive SARS-CoV-2 PCR result OR 11.0 (CI: 7.2-18.0, p Conclusions: The prevalence of anti-SARS-CoV-2 nucleocapsid IgG among HCWs was lower than in the general population. Staff working in clinical areas were not at increased risk when compared to staff working in non-clinical areas

Anti-spike antibody response based on COVID-19 result, sex and age.

Box plots of anti-Spike IgG S/Co ratio at first (A) and second (B) post-vaccination test between those with positive and negative SARS-CoV-2 test results. Anti-Spike IgG S/Co ratio at first and second post-vaccination testing by SARS-CoV-2 result by sex (C) and age category [n = 968] (D). SARS-CoV-2 PCR re-test was performed after the seroprevalence study and initiation of vaccination | PV = post vaccination.</p

Anti-spike antibody response at second and third vaccine doses.

Box plots of anti-spike IgG S/Co ratio at first (A) and second (B) post-vaccination test between those who received a second vaccine dose and those who did not receive two doses. Anti-Spike IgG S/Co ratio at first (C) and second (D) post-vaccination testing between participants receiving three vaccine doses and those not receiving three doses. | PV = post vaccination.</p

Frequency of side effects of vaccination.

IntroductionFollowing the coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, vaccination became the main strategy against disease severity and even death. Healthcare workers were considered high-risk for infection and, thus, were prioritised for vaccination.MethodsA follow-up to a SARS-CoV-2 seroprevalence study among clinical and non-clinical HCWs at the Aga Khan University Hospital, Nairobi, we assessed how vaccination influenced SARS-CoV-2 anti-spike IgG antibody responses and kinetics. Blood samples were drawn at two points spanning 6 to 18 months post-vaccination, and SARS-CoV-2 spike antibody levels were determined by enzyme-linked immunosorbent assay.ResultsAlmost all participants, 98% (961/981), received a second vaccine dose, and only 8.5% (83/981) received a third dose. SARS-CoV-2 spike IgG antibodies were detected in 100% (961/961) and 92.7% (707/762) of participants who received two vaccine doses, with the first and second post-vaccine test, respectively, and in 100% (83/83) and 91.4% (64/70) of those who received three vaccine doses at the first and second post-vaccine test, respectively. Seventy-six participants developed mild infections, not requiring hospitalisation even after receiving primary vaccination. Receiving three vaccine doses influenced the anti-spike S/Co at both the first (pDiscussion and conclusionFollowing the second dose of primary vaccination, all participants had detectable anti-spike antibodies. The observed mild breakthrough infections may have been due to emerging SARS-CoV-2 variants. Findings suggest that although protective antibodies are induced, vaccination protected against COVID-19 disease severity and not necessarily infection.</div

Anti-spike IgG S/Co ratio at second post-vaccination testing and COVID-19 test.

Stratified by sex (S1a) and age category (S1b) [age n = 968]. (JPG)</p