Within-Subject Interlaboratory Variability of QuantiFERON-TB Gold In-Tube Tests
Abstract
Background: The QuantiFERONH(registered trademark)-TB Gold In-Tube test (QFT-GIT) is a viable alternative to the tuberculin skin test (TST) for detecting Mycobacterium tuberculosis infection. However, within-subject variability may limit test utility. To assess variability we compared results from the same subjects when QFT-GIT enzyme-linked immunosorbent assays (ELISAs) were performed in different laboratories. Methods: Subjects were recruited at two sites and blood was tested in three labs. Two labs used the same type of automated ELISA workstation, 8-point calibration curves, and electronic data transfer. The third lab used a different automated ELISA workstation, 4-point calibration curves, and manual data entry. Variability was assessed by interpretation agreement and comparison of interferon-gamma (IFN-gamma) measurements. Data for subjects with discordant interpretations or discrepancies in TB Response >0.05 IU/mL were verified or corrected, and variability was reassessed using a reconciled dataset. Results: Ninety-seven subjects had results from three labs. Eleven (11.3%) had discordant interpretations and 72 (74.2%) had discrepancies .0.05 IU/mL using unreconciled results. After correction of manual data entry errors for 9 subjects, and exclusion of 6 subjects due to methodological errors, 7 (7.7%) subjects were discordant. Of these, 6 (85.7%) had all TB Responses within 0.25 IU/mL of the manufacturer's recommended cutoff. Non-uniform error of measurement was observed with greater variation in higher IFN-c measurements. Within-subject standard deviation for TB Response was as high as 0.16 IU/mL, and limits of agreement ranged from -0.46 to 0.43 IU/mL for subjects with mean TB Response within 0.25 IU/mL of the cutoff. Conclusion: Greater interlaboratory variability was associated with manual data entry and higher IFN-c measurements. Manual data entry should be avoided. Because variability in measuring TB Response may affect interpretation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 06, 2012
- Accession Number
- ADA567099
Entities
People
- Brandon H. Campbell
- Carlos Barrera
- Donald J. Goodwin
- Jamaria Bohanon
- Kevin B. West
- Lanette R. Hamilton
- Laura J. Daniels
- Laura Racster
- Stella O. Chuke
- William C. Whitworth
Organizations
- United States Air Force School of Aerospace Medicine