TABLE 1.
Specifications of the KCDC IFA and four commercial kits from companies A to Da
| Assay | Type of assay | Diagnostic criteria | Detailed explanation | Reference(s) |
|---|---|---|---|---|
| KCDC | IFA | Cutoff values of ≥1:16 for IgM and ≥1:256 for IgG; ≥4-fold increase in IgM or IgG titers | Separate detection of IgM and IgG against 4 O. tsutsugamushi antigen strains (Gilliam, Karp, Kato, and Boryong) | 3, 5 |
| Company A | IFA | Cutoff value of ≥1:40 | Detection of total immunoglobulins (IgM/IgG/IgA) against 3 O. tsutsugamushi antigen strains (Boryong, Karp, and Gilliam) | 9 |
| Company B | IFA | Cutoff values of ≥1:64 for IgM and ≥1:128 for IgG | Separate detection of IgM and IgG against 4 O. tsutsugamushi antigen strains (Gilliam, Karp, Kato, and Boryong) | 6 |
| Company C | RDT | Positive or negative | Detection of IgM/IgG against 5 O. tsutsugamushi antigen strains (Gilliam, Karp, Kato, Kangwon, and Boryong) | 10 |
| Company D | RDT | Positive or negative | Detection of total immunoglobulins against 3 O. tsutsugamushi antigen strains (Gilliam, Karp, and Kato) | 8, 10 |
a
KCDC, Korea Centers for Disease Control and Prevention; IFA, indirect immunofluorescence assay; RDT, immunochromatography-based rapid diagnostic test.