Comparative Analysis of Capillary vs Venous Blood for Serologic Detection of SARS-CoV-2 Antibodies by RPOC Lateral Flow Tests

Abstract

A comparison of rapid point of care serology tests using finger prick and venous blood was done on 278 participants. In a laboratory setting, IgG sensitivity neared 100%; however, IgG sensitivity dramatically dropped (82%) in field testing. Possible factors include finger prick volume variability, hemolysis, cassette readability and operator training.

COVID-19 Antibody Detecting Rapid Diagnostic Tests Show High Cross-Reactivity When Challenged with Pre-Pandemic Malaria, Schistosomiasis and Dengue Samples

“…There were no control groups (e.g., healthy individuals or confirmed COVID-19 patients) for comparison, and in view of the ethical clearance it was not possible to exclude other potential causes of cross-reactivity or interfering substances such as the presence of rheumatoid factor, anti-nuclear antibodies, haemoglobin or concurrent malaria antibodies in schistosomiasis or dengue samples. Further, only a fraction of COVID-19 Ab RDTs marketed and one lot per product were assessed, whereas lot-to-lot variations may occur [ 8 ]. In view of limited accessible sample volumes, extra COVID-19 diagnostic testing (e.g., with other EIA platforms) was not possible.…”

“…A similar impact can be expected in areas endemic for schistosomiasis and dengue. Adding to the challenges of seroprevalence studies with COVID-19 Ab RDTs is the use of capillary blood (the preferred specimen for seroprevalence studies in LMICs [ 10 ]), which needs further study as to its accuracy, particularly when used in field settings [ 6 , 8 , 13 ]. As to the applications of triage and COVID-19 disease diagnosis in LMICs, the similarity of its early clinical presentations with those of malaria and dengue and the potential co-occurrence of these diseases present additional problems [ 25 , 32 , 40 , 44 , 69 ].…”

“…Although not a study objective (and not systematically assessed), we observed shortcomings in products’ instructions for use (not mentioning the detecting antigen for 11/13 products), manufacturing (bacterial contamination of the buffer vial, errors of cassette assembly and labeling) and performance (weak control and test lines). These shortcomings can seriously affect the usability of the products in the field; they have been noted before and may be caused by rapid development in view of high customer demand and insufficient regulatory oversight [ 4 , 8 , 70 ].…”

“…In low-and middle-income countries (LMICs), COVID-19 Ab RDTs have also been deployed for triage, diagnosis and contact tracing [10][11][12]. Specificity testing of COVID-19 Ab RDTs so far has focused on seasonal coronaviruses (NL63, HKU1, 229E, OC43), SARS-CoV, cytomegalovirus, Epstein-Barr virus, human hepatitis B virus, Mycoplasma pneumoniae and parvovirus infection in addition to interfering conditions (rheumatoid factor, autoimmune pathologies and hyperglobulinemia) [8,[13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Tropical diseases such as malaria, dengue, schistosomiasis and human African trypanosomiasis are well-known for their cross-reactivity with HIV-1 antibody LFA RDTs and malaria antigen RDTs [27][28][29][30].…”

“…Compared to laboratory platforms (enzyme immunoassays (EIA) and chemiluminescence assays (CLIA)), COVID-19 Ab RDTs have simple logistics, require relatively little training, have a short turnaround time, are easily scalable and are amenable to self-testing. As such, they are therefore preferred tools for seroprevalence studies [ 5 , 8 , 9 ], despite the fact that the WHO recommends the use of enzyme immunoassays for seroprevalence studies [ 1 ]. In low- and middle-income countries (LMICs), COVID-19 Ab RDTs have also been deployed for triage, diagnosis and contact tracing [ 10 , 11 , 12 ].…”