title: Analysis of liquid bead microarray antibody assay data for epidemiologic studies of pathogen-cancer associations.
abstract: BACKGROUND
  Liquid bead microarray antibody (LBMA) assays are used to assess pathogen-cancer associations. However, studies analyze LBMA data differently, limiting comparability.
  
  
  METHODS
  We generated 10,000 Monte Carlo-type simulations of log-normal antibody distributions (exposure) with 200 cases and 200 controls (outcome). We estimated type I error rates, statistical power, and bias associated with t-tests, logistic regression with a linear exposure and with the exposure dichotomized at 200 units, 400 units, the mean among controls plus two standard deviations, and the value corresponding to the optimal sensitivity and specificity. We also applied these models, and data visualizations (kernel density plots, receiver operating characteristic (ROC) curves, predicted probability plots, and Q-Q plots), to two empirical datasets to assess the consistency of the exposure-outcome relationship.
  
  
  RESULTS
  All strategies had acceptable type I error rates (0.03 ≤ P ≤ 0.048), except for the dichotomization according to optimal sensitivity and specificity, which had a type I error rate of 0.27. Among the remaining methods, logistic regression with a linear predictor (Power=1.00) and t-tests (Power=1.00) had the highest power to detect a mean difference of 1.0 MFI (median fluorescence intensity) on the log scale and were unbiased. Dichotomization methods upwardly biased the risk estimates.
  
  
  CONCLUSIONS
  These results indicate that logistic regression with linear predictors and unpaired t-tests are superior to logistic regression with dichotomized predictors for assessing disease associations with LBMA data. Logistic regression with continuous linear predictors and t-tests are preferable to commonly used LBMA dichotomization methods.
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA; Department of Epidemiology, School of Public Health, University of Washington, F-263 Health Sciences Building, Box 357236, Seattle, WA 98195-7236, USA. Electronic address: dvc2@uw.edu.
authors.forename: Danny V
authors.initials: DV
authors.lastname: Colombara
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA; Department of Biostatistics, School of Public Health, University of Washington, F-600 Health Sciences Building, Box 357232, Seattle, WA 98195-7232, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Hughes
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA; Department of Epidemiology, School of Public Health, University of Washington, F-263 Health Sciences Building, Box 357236, Seattle, WA 98195-7236, USA.
authors.forename: Andrea N
authors.initials: AN
authors.lastname: Burnett-Hartman
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, F-263 Health Sciences Building, Box 357236, Seattle, WA 98195-7236, USA.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Hawes
authors.affiliation: Human Biology Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA; Department of Microbiology, School of Medicine, University of Washington, Box 357735, Seattle, WA 98195-7735, USA.
authors.forename: Denise A
authors.initials: DA
authors.lastname: Galloway
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA; Department of Epidemiology, School of Public Health, University of Washington, F-263 Health Sciences Building, Box 357236, Seattle, WA 98195-7236, USA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Schwartz
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, 1518 Clifton Road, NE, Atlanta, GA 30322, USA; Winship Cancer Institute, Emory University, 1365-C Clifton Road NE, Atlanta, GA 30322, USA.
authors.forename: Roberd M
authors.initials: RM
authors.lastname: Bostick
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., P.O. Box 19024, Seattle, WA 98109-1024, USA; Department of Epidemiology, School of Public Health, University of Washington, F-263 Health Sciences Building, Box 357236, Seattle, WA 98195-7236, USA; Centre for Public Health Research, Massey University, PO Box 756, Wellington 6140, New Zealand.
authors.forename: John D
authors.initials: JD
authors.lastname: Potter
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, F-263 Health Sciences Building, Box 357236, Seattle, WA 98195-7236, USA; University of Washington Center for AIDS and STD, 325 9th Ave, Campus Box 359931, Seattle, WA 98104, USA.
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Manhart
mesh_terms: D000906:Antibodies / Q000276:immunology*; D001681:Biological Assay / Q000379:methods*; D016022:Case-Control Studies; D003627:Data Interpretation, Statistical; D004784:Environmental Monitoring / Q000379:methods; D016021:Epidemiologic Studies; D006801:Humans; D015233:Models, Statistical; D008962:Models, Theoretical; D009010:Monte Carlo Method; D009369:Neoplasms / Q000276:immunology* / Q000382:microbiology*; D012680:Sensitivity and Specificity
chemical_list: D000906:Antibodies
keywords: Cut-point; Dichotomization; Liquid bead microarray antibody assay; Median fluorescence intensity; Visualization