An ELISA assay using a combination of recombinant proteins from multiple strains of Orientia tsutsugamushi offers an accurate diagnosis for scrub typhus

Table 1 Description of clinical samples included in the ELISA evaluation^a

Diagnosis	# of samples	Case definition (# of samples)
Scrub typhus^b	78	IgG or IgM or both ≥400 (61), or 4-fold increase in IgG or IgM titer between convalescent and acute specimens (6), or PCR positive only^d (5), or PCR positive and 4-fold increase in titer (6)
Dengue	11	NS1, or IgG or IgM rapid test positive
Murine typhus	2	single IFA IgG and/or IgM titer ≥400, or a 4-fold increase in IgG or IgM titer
leptospirosis	16	single IFA IgG or IgM titer ≥400, or a 4-fold increase in titer of IgG or IgM, or positive PCR for LipL32
Other bacteremia	3	Bacteria culture positive
Co-infection (Scrub typhus and others)^c	8	IgG or IgM ≥ 400 (7), 4-fold increase in IgG and IgM titer between convalescent and acute specimens (1)
unknown	130	Negative by all above

^aSamples were determined for the cause of infection using the criteria listed
^bFive different criteria were applied to determine scrub typhus positive. A sample is considered scrub typhus positive if it is positive by any of the 5 criteria. Numbers in parentheses represent number of cases defined by respective criterion
^cThe same criteria to identify scrub typhus positive were applied to co-infection samples
^dThe 47 kDa or 56 kDa gene was used as targets for PCR

ISSN: 1471-2334