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Results were essentially unchanged when the Cox Proportional Hazards regression model was repeated ( a ) using 1 medication episode per patient ( n = 1028 ) , the one with which the patient was treated first , ( b ) using 1703 treatment episodes , including episodes where patients simultaneously initiated 2 or more treatment episodes , ( c ) using the time elapsed between medication initiation and patients ' enrollment in the study , as a proxy for potential " sponsor-related physician bias , " ( d ) using a medication gap > 14 days to assess robustness of the > 30-day medication gap used to signal medication discontinuation , and ( e ) using ITT analysis , with 2488 treatment episodes , thus not requiring initiators to have continued in the study for at least 1 year following medication initiation . To help address potential " period bias , " we included time to initiation on the index antipsychotic from the starting date of the US-SCAP study as a covariate in the Cox Proportional Hazards regression model , and in the propensity score method . The p values are calculated via the log-rank test . To that end , we performed an additional sensitivity analysis in which the time from patient 's enrollment in US-SCAP to the time of patient 's initiation on the index medication was used as a covariate in the Cox Proportional Hazards regression model . Localized expression of 22 H. asinina ESTs in the juvenile mantle revealed by whole mount in situ hybridization ( WMISH ) . Only the NTERA-2 embryonal carcinoma line shows an atypical histocompatibility profile , being homozygous at all tested loci . For the main analysis , all treatment group comparisons were made using ( a ) Kaplan-Meier survival analysis ( log-rank test ) , ( b ) Cox Proportional Hazards regression model , and ( c ) propensity score-adjusted bootstrap resampling method with 1000 iterations . In addition , 5 sensitivity analyses were performed ( using the Cox Proportional Hazards regression model with the identified covariates ) to address other potential sample selection biases . To help address potential selection bias of the treatment groups , we identified , a priori , a set of available covariates that were used in the Cox Proportional Hazards regression model ( covariates are listed later in this section ) .