Cancer diagnosis does not impact COVID-19 IgG seroconversion rates
medwireNews: SARS-CoV-2-specific immunoglobulin (Ig)G antibody detection rates do not differ significantly between people with cancer and healthy individuals who have either confirmed or suspected COVID-19, Italian study data show.
Giuseppe Curigliano (European Institute of Oncology IRCCS, Milan) and colleagues used the 2019-nCoV IgG/IgM Rapid Test Cassette (PRIMA Lab SA, Balerna, Switzerland) to screen 61 individuals with cancer and 105 healthcare workers without cancer for SARS-CoV-2-specific IgG antibodies between 30 March and 11 May 2020.
They say their results show that rapid testing “for antibody detection can be a complement to RNA RT-PCR [reverse transcription-polymerase chain reaction] testing for the diagnosis of COVID-19, especially in those situations where the knowledge of the COVID-19 status is rapidly mandatory for specific clinical decisions.”
Among the study participants, 51.8% had a confirmed COVID-19 diagnosis by RT-PCR testing, 36.2% had a clinically suspected COVID-19, and 12.0% were patients with cancer at high risk for infection.
The researchers report in the Annals of Oncology that, overall, 46.9% of study participants had a positive SARS-CoV-2 IgG test.
For individuals with confirmed COVID-19, the IgG positivity rate was 83.8%, with no significant difference between patients with cancer and controls, at 87.9% versus 80.5%.
There was also no significant difference in IgG positivity rates between the patients with cancer and controls who had a negative SARS-CoV-2 RT-PCR result, at 10.7% versus 7.0%.
“This finding suggests that a majority of participants suspected for COVID-19 actually were not infected with SARS-CoV-2,” Curigliano et al remark. However, they also acknowledge that the low rates in these individuals “may be related to a false negative rate of our assay or insufficient time for participants to mount an IgG antibody response detectable by means [of] rapid test.”
The median time from SARS-CoV-2 diagnosis to IgG detection was 23 days among the cancer patients and 28 days among the healthcare workers, a nonsignificant difference.
The investigators note that age, sex, comorbidity, and symptom intensity did not significantly affect rate and time of IgG antibody response, but point out that the majority (79.2%) of participants presented with mild disease. “[T]hus these data may not reflect antibody response in moderate or severe COVID-19,” they say.
Curigliano and co-authors conclude: “In [a] vulnerable population such as cancer patients, confirming suspected COVID-19 cases as early as possible with the help of serological testing could reduce exposure risk and help [optimize] diagnostic and therapeutic algorithms.”
They now plan to prospectively follow their patient population and “retest for IgG by both quantitative and qualitative assays after three and six months in order to measure time and level of immunization.”
medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2020 Springer Healthcare Ltd, part of the Springer Nature Group
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