. Author manuscript; available in PMC: 2018 Jul 1.

Published in final edited form as: Stat Methods Med Res. 2017 Oct 3;28(2):599–612. doi: 10.1177/0962280217732597

Table 1.

A summary of the true exposure-outcome relationship scenarios considered in the simulation studies.

Scenario	Binary outcome: Preterm birth (<37 weeks gestational age at delivery)^a	Continuous outcome: Standardized Bayley-III score of infant at 12 months
(i) No effects	P(Y₁)=0.12	E(Y₂)=0
(ii) A class of drugs has a subtle effect	P(Y₁)=0.12+0.04*PI (OR_PI=1.40)	E(Y₂)=0–0.3*PI
(iii) One ARV drug has a moderate effect
(a) more common ARV drug (>15% exposure)	P(Y₁)=0.12+0.09*LPV/r (OR_LPV/r=1.95)	E(Y₂)=0–0.5*LPV/r
(b) less common ARV drug (5–15% exposure)	P(Y₁)=0.12+0.09*ABC (OR_ABC=1.95)	E(Y₂)=0–0.5*ABC
(c) rarely used ARV drug (<5% exposure)	P(Y₁)=0.12+0.09*EFV (OR_EFV=1.95)	E(Y₂)=0–0.5*EFV
(iv) Two drugs from the same drug class have moderate effects, but in opposite directions	P(Y₁)=0.12+0.09* LPV/r – 0.05*DRV (OR_LPV/r=1.95, OR_DRV=0.55)	E(Y₂)=0–0.5LPV/r + 0.5DRV

ABC: abacavir; DRV: darunavir; E: expected value; EFV: efavirenz; LPV/r: ritonavir-boosted lopinavir; OR_ABC: odds ratio comparing ABC-exposed to ABC-unexposed; OR_DRV: odds ratio comparing DRV-exposed to DRV-unexposed: OR_EFV: odds ratio comparing EFV-exposed to EFV-unexposed; OR_LPV/r: odds ratio comparing LPV/r-exposed to LPV/r-unexposed; OR_PI: odds ratio comparing PI-exposed to PI-unexposed; P: probability; PI: protease inhibitor; Y₁: preterm birth; Y₂: standardized Bayley-III cognitive score.

The corresponding logistic models are: (i) logit(P(Y₁))= −1.9924; (ii) logit(P(Y₁))=−1.9924)0.3365*PI; (iii) logit(P(Y₁))=−1.9924)0.6678*X_j (where X_j indicates LPV/r, ABC, or EFV); and (iv) logit(P(Y₁))=−1.9924)0.6678*LPV/r – 0.5978*DRV. Note that LPV/r and DRV are mutually exclusive (women are never exposed to both drugs simultaneously).