Table 4

Modification* by HCQ of HRs for the association of pregnancy and lupus flares: the Hopkins Lupus Cohort, 1987–2015 (n=1349)

Patients exposed to HCQPatients unexposed to HCQ
FlaresPYCrude incidence per 100 PYHR† (95% CI)FlaresPYCrude incidence per 100 PYHR†  (95% CI)
 12-month postpartum period
  Not pregnant/postpartum14583843.038.01.0 (ref)7881740.345.31.0 (ref)
  Pregnancy52123.442.11.26 (0.88 to 1.69)8297.384.31.83 (1.34 to 2.45)
  12 months postpartum75212.235.31.02 (0.72 to 1.32)73158.746.00.98 (0.67 to 1.31)
 3-month postpartum period
  Not pregnant/postpartum15103967.338.11.0 (ref)8261819.045.41.0 (ref)
  Pregnancy52123.442.11.24 (0.86 to 1.73)8297.384.31.84 (1.37 to 2.44)
  3 months postpartum2351.644.61.25 (0.71 to 1.87)3544.079.51.63 (1.04 to 2.39)
 12-month postpartum period
  Not pregnant/postpartum17653843.045.91.0 (ref)8761740.350.31.0 (ref)
  Pregnancy64123.451.91.35 (0.92 to 1.81)7697.378.11.59 (1.17 to 2.09)
  12 months postpartum100212.247.11.13 (0.88 to 1.44)70158.744.10.91 (0.64 to 1.20)
 3-month postpartum period
  Not pregnant/postpartum18343967.346.21.0 (ref)9141819.050.21.0 (ref)
  Pregnancy64123.451.91.32 (0.91 to 1.79)7697.378.11.61 (1.20 to 2.10)
  3 months postpartum3151.660.11.53 (0.96 to 2.25)3244.072.71.45 (0.87 to 2.11)
  • *To test whether effects were similar for HCQ users and non-users, an interaction term between each medication with the exposure was included in the model. Effect measure modification was determined by likelihood ratio test (α=0.20).

  • †Estimated by stratified Cox model, a conditional model that does not assume independence of multiple events of flares and allows different baseline hazards based on the number of previous flares a patient experienced.

  • ‡Flare defined as change in ≥1 from PGA score at previous visit.

  • §Flare defined as change in ≥4 from SELENA-SLEDAI score at previous visit.

  • HCQ, hydroxychloroquine; PGA, Physician Global Assessment of disease activity; PY, person-years; SLE, systemic lupus erythematosus; SLEDAI, SLE Disease Activity Index.