None of 28 infected HCWs who had the RT-PCR more than 50?days ago tested positive for antibodies. carried out a seroprevalence survey of healthcare workers (HCW) working in three Government run hospitals in Mumbai. Pan immunoglobulin Elecsys Anti-SARS-CoV-2 Assay (Roche Diagnostics, Rotkreuz, Switzerland) using recombinant protein representing the nucleocapsid (N) antigen in double antigen sandwich assay format was done after informed consent. This test has a specificity of 99.8% and 100% sensitivity for patients, fourteen days post-PCR confirmation. The result is given as a cut off index (CoI), and is then interpreted either as reactive/positive (CoI??1.0) or non-reactive/negative (CoI? ?1.0) [5]. We did not test for the antibodies against S antigen. A pretested, validated questionnaire in local language was used to collect data on demographic details and symptoms. The study was approved by Institutional Ethics Committee of the JJ group and Grant Medical College, Mumbai, India. Among the 801 HCWs who got tested, seroprevalence was 11.1%. Males (13.5% vs. 8.9% in females) and ancillary workers (18.5% vs 6.9% in doctors and nurses) were more likely to be seropositive (Table 1 ). Table 1 Seroprevalence as per different demographic and comorbidity characteristics. thead th rowspan=”1″ colspan=”1″ Group /th th rowspan=”1″ colspan=”1″ All /th th rowspan=”1″ colspan=”1″ Sero (?) /th th rowspan=”1″ colspan=”1″ Sero (+) /th th rowspan=”1″ colspan=”1″ % (+) /th th rowspan=”1″ colspan=”1″ 95% CI /th th rowspan=”1″ colspan=”1″ p value Odds ratio /th /thead All8017128911.19.1C13.5 br / br / em Occupation /em Ancillary workers2922385418.514.5C23.3Odds?=?0.227Doctors201187147.04.2C11.4OR?=?2.65Nurses308287216.84.5C10.2OR?=?2.71 br / br / em Gender /em Male3863345213.510.4C17.3p?=?0.04 OR?=?1.51Female415378378.96.5C12.1 br / br / em Age L-Tyrosine group /em 20C40?years413372419.97.4C13.2p?=?0.54 OR?=?0.80340C60?years3803334712.49.4C16.1 =60?years87112.52.2C47.1 br / br / em Comorbidities /em None6826047811.49.3C14.10.49Single1039498.74.5C16.00.62Multiple1614212.52.2C37.3Cancer54120.02.0C64.00.94Immunosuppression119218.24.0C48.90.45Asthma353238.62.2C23.10.67Cardiac problems484448.32.8C20.10.56Diabetes mellitus383537.92.0C21.50.56 Open in a separate window There was significantly higher seroprevalence in those previously diagnosed with COVID-19 with a positive PCR test compared to those who had not been tested by RT-PCR; 29% (CI 19.2C41.4) compared to 9.6% (CI 7.7C12). Sixty-two (7.74%) had been previously diagnosed with RT PCR test for SARS-CoV-2. Of these, 44 (71%) were seronegative. Individuals who were symptomatic in the last 30?days with any of the symptoms associated with COVID-19 had a significantly higher seropositive rate; 16.8% (CI 11.8C23.2) compared to 9.6% (CI 7.6C12.2). Sub-analysis of the various symptoms indicates that only loss of smell or taste and presence of non-specific febrile illness in the last 30?days were significant variables associated with higher seroprevalence. None of the other symptoms associated with COVID-19 were statistically significant (Table 2 ). Table 2 Seroprevalence and associated factors. thead th rowspan=”1″ colspan=”1″ Group /th th rowspan=”1″ colspan=”1″ All /th th rowspan=”1″ colspan=”1″ Sero (?) /th th rowspan=”1″ colspan=”1″ Sero (+) /th th rowspan=”1″ colspan=”1″ +ve (%) /th th rowspan=”1″ colspan=”1″ 95% CI /th th rowspan=”1″ colspan=”1″ p value /th /thead em PCR positive individuals /em COVID PCR (+)62441829.019.2C41.40.000003 br / OR?=?3.02COVID PCR (?)739668719.67.7C12.0Symptomatic in last month1671392816.811.8C23.20.0001 br / OR?=?2.655Asymptomatic in last month634573619.67.6C12.2 br / br / em Symptoms associated with seropositivity /em Loss of taste/smell104660.031.2C83.30.0003 br / OR?=?2.71No loss of taste/smell7917088310.58.5C12.8Aadorable Febrile Illness28151346.429.5C64.20.000002 br / OR?=?1.51No acute Febrile Illness773697769.87.9C12.1Any Acute Respiratory Illness97831414.48.7C22.90.26No acute Respiratory Illness7046297510.78.6C13.2Aadorable Respiratory Illness C SARI1613318.85.8C43.80.59Aadorable Respiratory Illness C ILI81701113.67.6C22.9Non-specific illness90781213.37.6C22.00.47No Non-specific illness7116347710.88.7C13.3Aadorable Gastric/enteric illness87112.50.1C49.20.83No acute gastric/enteric illness7937058811.19.1C13.5Eye Redness121118.30.0C37.50.84No Vision Redness7897018811.29.1C13.6Skin rash98111.10.0C45.70.91No skin rash7928870488.986.5C90.9 Open L-Tyrosine in a separate window Subjects who had visited a fever L-Tyrosine clinic in the last 30?days had a significantly higher seroprevalence; 20.5% (CI 14.4C28.2) compared to 9.3% (CI 7.3C11.7). Individuals with a family member living in the same house diagnosed with COVID-19 had a significantly higher seroprevalence; 18.9% (CI 11.5C29.4) compared to 10.3% (CI 8.3C12.8). Using a COVID-19 patient living within 50?m of the individuals residence was not a significant factor for increased seroprevalence (see Table 3 ). Table 3 Seroprevalence based on exposure. thead th rowspan=”1″ colspan=”1″ Group /th th rowspan=”1″ colspan=”1″ All /th th rowspan=”1″ colspan=”1″ Sero (?) /th th rowspan=”1″ colspan=”1″ Sero (+) /th th rowspan=”1″ colspan=”1″ (+) % /th th rowspan=”1″ colspan=”1″ 95% CI /th th rowspan=”1″ colspan=”1″ p value Odds ratio /th /thead em Risk/exposure characteristics /em Visited Fever clinic1321052720.514.4C28.20.0002 OR?=?2.52Not visited fever clinic669607629.37.3C11.7Household person positive74601418.911.5C29.40.02 OR?=?2.03No household person positive7276527510.38.3C12.8Neighbourhood person positive3973484912.39.4C16.00.27No Neighbourhood person positive404364409.97.3C13.2 Open in a separate windows Duration between positive RT-PCR test Rabbit Polyclonal to CKMT2 and serological testing ranged from 15 to 49?days for 34 (54.8%), and 50?days in 28 subjects. Upto 28?days after a positive PCR test, 90% of subjects were found to be seropositive. This reduced to less than half over next two weeks (38.5%) between 29 and 42?days. This further reduced to less than 15% for subjects who were tested between 43 and 49?days of their positive RT-PCR. None of the 28 infected HCWs who had had the RT-PCR more than 50?days ago tested positive for the antibodies. Of the people who had never been RT PCR positive, 9.6% had antibodies (Table 4 ). The mean antibody levels of people who had never been tested for RT PCR were 26.77 CoI (28.47 CoI in those with RT PCR test positive). Table 4 Weekwise anti SARS-CoV-2 antibody levels in Healthcare workers in Mumbai, India. thead th rowspan=”1″ colspan=”1″ Days after (+)ve RT-PCR Test /th th rowspan=”1″ colspan=”1″ No. Of persons /th th rowspan=”1″ colspan=”1″ Positives# /th th rowspan=”1″ colspan=”1″ Antibody levels mean (std dev) COI /th th rowspan=”1″ colspan=”1″ Outliers* n (values) /th /thead 15C21531.01 (1.61)1 (14.26)22C2811931.7 (31.3)1 (0.08)29C35720.93 (1.81)1 (73)36C42610.1 (0.1)1 (12.91)43C49610.1 (0.03)1 (28.93)50C56900.07 (0.01)0 561800.08 (0.01)2 (0.92, 0.12) Open in a separate windows #COI? ?1 is.