Inter- and intra-operator variability in the reading of indirect immunofluorescence assays for the serological diagnosis of scrub typhus and murine typhus.

Journal article

Inter- and intra-observer variation was examined among six microscopists who read 50 scrub typhus (ST) and murine typhus (MT) indirect immunofluorescence assay (IFA) immunoglobulin M (IgM) slides. Inter-observer agreement was moderate (κ = 0.45) for MT and fair (κ = 0.32) for ST, and was significantly correlated with experience (P = 0.03 and P = 0.004, respectively); κ-scores for intra-observer agreement between morning and afternoon readings (range = 0.35-0.86) were not correlated between years of experience for ST and MT IFAs (Spearman's ρ = 0.31, P = 0.54 and P = 0.14, respectively; P = 0.78). Storage at 4°C for 2 days showed a change from positive to negative in 20-32% of slides. Although the titers did not dramatically change after 14 days of storage, the final interpretation (positive to negative) did change in 36-50% of samples, and it, therefore, recommended that slides should be read as soon as possible after processing.

Authors: Phetsouvanh, R; Thojaikong, T; Phoumin, P; Sibounheuang, B; Phommasone, K

• Publication status: Published
• Journal: American journal of tropical medicine and hygiene
• Volume: 88
• Issue: 5
• Pages: 932-936
• Publication date: 2013-05-01
• DOI: 10.4269/ajtmh.12-0325
• EISSN: 1476-1645
• ISSN: 0002-9637
• Language: English
• Keywords: Immunoglobulin M; Fluorescent Antibody Technique, Indirect; Male; Observer Variation; Female; Scrub Typhus; Orientia tsutsugamushi; Immunoglobulin G; Rickettsia typhi; Typhus, Endemic Flea-Borne; Young Adult; Adolescent; Humans; Adult