Addressing ceiling effects in health status measures: a comparison of techniques applied to measures for people with HIV disease.
OBJECTIVE
To compare different approaches to address ceiling effects when predicting EQ-5D index scores from the 10 subscales of the MOS-HIV Health Survey.


METHODS
Data were collected from an HIV treatment trial. Statistical methods included ordinary least squares (OLS) regression, the censored least absolute deviations (CLAD) approach, a standard two-part model (TPM), a TPM with a log-transformed EQ-5D index, and a latent class model (LCM). Predictive accuracy was evaluated using percentage of absolute error (R(1)) and squared error (R(2)) predicted by statistical methods.


RESULTS
A TPM with a log-transformed EQ-5D index performed best on R(1); a LCM performed best on R(2). In contrast, the CLAD was worst. Performance of the OLS and a standard TPM were intermediate. Values for R(1) ranged from 0.33 (CLAD) to 0.42 (TPM-L); R(2) ranged from 0.37 (CLAD) to 0.53 (LCM).


CONCLUSIONS
The LCM and TPM with a log-transformed dependent variable are superior to other approaches in handling data with ceiling effects.
Huang
I-Chan
IC
Department of Epidemiology and Health Policy Research, College of Medicine, University of Florida, Gainesville, FL, USA.
Frangakis
Constantine
C
Atkinson
Mark J
MJ
Willke
Richard J
RJ
Leite
Walter L
WL
Vogel
W Bruce
WB
Wu
Albert W
AW
D019380:Anti-HIV Agents / Q000627:therapeutic use; D003627:Data Interpretation, Statistical; D020008:Delavirdine / Q000627:therapeutic use; D015658:HIV Infections / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D015497:HIV-1 / Q000187:drug effects; D006801:Humans; D015233:Models, Statistical; D017060:Patient Satisfaction; D011788:Quality of Life; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use; D018434:Sickness Impact Profile; D012959:Socioeconomic Factors
D019380:Anti-HIV Agents; D018894:Reverse Transcriptase Inhibitors; D020008:Delavirdine