title: Bayesian inference for skew-normal mixture models with left-censoring.
abstract: Assays to measure concentration of antibody after vaccination are often subject to left-censoring due to a lower detection limit (LDL), leading to a high proportion of observations below the detection limit. Not accounting for such left-censoring appropriately can lead to biased parameter estimates. To properly adjust for left-censoring and a high proportion of observations at LDL, this article proposes a mixture model combining a point mass below LDL and a Tobit model with skew-elliptical error distribution. We show that skew-elliptical distributions, where the skew-normal and skew-t are special cases, have great flexibility for simultaneously handling left-censoring, skewness, and heaviness in the tails of a distribution of a response variable with left-censored data. A Bayesian procedure is used to estimate model parameters. Two real data sets from a study of the measles vaccine and an HIV/AIDS study are used to illustrate the proposed models.
authors: Department of Epidemiology and Biostatistics, College of Public Health, University of South Florida, Tampa, Florida 33612, USA. gdagne@health.usf.edu
authors: Getachew A
authors: GA
authors: Dagne
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy / Q000821:virology; D044966:Anti-Retroviral Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D000914:Antibodies, Viral / Q000097:blood; D001499:Bayes Theorem; D002986:Clinical Trials as Topic / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology; D006801:Humans; D007223:Infant; D057230:Limit of Detection; D008297:Male; D008457:Measles / Q000097:blood / Q000453:epidemiology / Q000517:prevention & control; D008458:Measles Vaccine / Q000276:immunology; D015233:Models, Statistical; D015588:Observer Variation; D012367:RNA, Viral / Q000097:blood; D019562:Viral Load / Q000187:drug effects
chemical_list: D044966:Anti-Retroviral Agents; D000914:Antibodies, Viral; D008458:Measles Vaccine; D012367:RNA, Viral
references: Nature. 1995 Jan 12;373(6510):123-6
references: 7816094
references: J Acquir Immune Defic Syndr. 2004 Nov 1;37(3):1358-66
references: 15483465
references: J Androl. 2002 Sep-Oct;23(5):629-34
references: 12185096
references: Stat Med. 2008 Sep 30;27(22):4489-501
references: 18465838
references: Biometrics. 1995 Dec;51(4):1570-8
references: 8589241
references: J Allergy Clin Immunol. 2008 Jul;122(1):22-8
references: 18602567
references: Epidemiology. 2010 Jul;21 Suppl 4:S25-34
references: 20386106
references: Biometrics. 1999 Jun;55(2):625-9
references: 11318225
references: Bioinformatics. 2002;18 Suppl 1:S96-104
references: 12169536
references: Pediatrics. 1995 Sep;96(3 Pt 1):447-50
references: 7651776
references: N Engl J Med. 1985 Aug 29;313(9):544-9
references: 4022091
references: Eur J Clin Microbiol Infect Dis. 2008 Jun;27(6):461-5
references: 18293018
references: Math Biosci. 1999 Aug;160(1):63-82
references: 10465932
references: Vaccine. 1996 Aug;14(12):1154-8
references: 8911013
references: Stat Med. 2001 Jan 15;20(1):33-45
references: 11135346
references: Environ Sci Technol. 2005 Oct 15;39(20):419A-423A
references: 16295833
references: Pediatr Infect Dis J. 2005 Dec;24(12):1083-8
references: 16371870
references: Biostatistics. 2010 Apr;11(2):317-36
references: 20110247
references: Pediatr Infect Dis J. 1991 Apr;10(4):303-11
references: 2062626
references: Ann Occup Hyg. 2011 Jan;55(1):97-112
references: 21177260
references: Chemosphere. 2010 Jun;80(1):7-12
references: 20416924