Table 3.
Subgroup interaction analyses in preterm infants with type 1 ROP, type 2 ROP
| Type 1 ROP | Type 2 ROP | Type 1 or Type 2 ROP | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Characteristic | Control, n = 28 No. (%) | rhEPO, n = 23 No. (%) | RR (95% CI) | Interaction P value | Control, n = 36 No. (%) | rhEPO, n = 20 No. (%) | RR (95% CI) | Interaction P value | Control, n = 64 No. (%) | rhEPO, n = 43 No. (%) | RR (95% CI) | Interaction P value |
| Sex | 0.391 | 0.022 | 0.021 | |||||||||
| Boys | 19/538 (3.5) | 10/549 (1.8) | 0.98 (0.96–1.00) | 23/538 (4.3) | 10/549 (1.8) * | 0.98 (0.96–1.00) | 42/538 (7.8) | 20/549 (3.6) * | 0.96 (0.93–0.99) | |||
| Girls | 9/340 (2.6) | 13/364 (3.6) | 1.01 (0.98–1.04) | 13/340 (3.8) | 10/364 (2.7) | 0.99 (0.96–1.02) | 22/340 (6.5) | 23/364 (6.3) | 1.00 (0.96–1.04) | |||
| Gestational age** | 0.295 | 0.016 | 0.012 | |||||||||
| < 28 weeks | 6/50 (12.0) | 7/65 (10.8) | 0.99 (0.86–1.13) | 3/50 (6.0) | 8/64 (12.5) | 1.07 (0.96–1.20) | 9/50 (18.0) | 15/64 (23.4) | 1.07 (0.89–1.30) | |||
| 28–296/7 weeks | 8/326 (2.5) | 10/362 (2.8) | 1.00 (0.98–1.03) | 16/326 (4.9) | 4/362 (1.1) * | 0.96 (0.94–0.99) | 24/326 (7.4) | 14/362 (5.3) | 0.96 (0.93–1.00) | |||
| 30–32 weeks | 14/502 (2.8) | 6/485 (1.2) | 0.98 (0.97–1.00) | 17/502 (3.4) | 8/485 (1.6) | 0.98 (0.96–1.00) | 31/502 (6.2) | 14/485 (2.9) * | 0.97 (0.94–0.99) | |||
| Birth weight** | 0.275 | 0.013 | 0.008 | |||||||||
| < 1000 g | 5/52 (9.6) | 10/63 (15.9) | 1.07 (0.94–1.24) | 7/52 (13.5) | 8/63 (12.7) | 0.99 (0.86–1.14) | 12/52 (23.1) | 18/63 (28.6) | 1.07 (0.87–1.34) | |||
| 1000–1499 g | 16/544 (2.9) | 12/644 (1.9) | 0.99 (0.97–1.01) | 23/544(4.2) | 8/644 (1.2) * | 0.97 (0.95–0.99) | 39/544 (7.2) | 20/644 (3.1) * | 0.96 (0.93–0.98) | |||
| ≥ 1,500 g | 7/282 (2.5) | 1/205 (0.5) | 0.98(0.96–1.00) | 6/282 (2.1) | 4/205 (2.0) | 1.00 (0.97–1.02) | 13/282 (4.6) | 5/205 (2.4) | 0.98 (0.95–1.01) | |||
Probability value is for interaction analysis in subgroups using the Mantel–Haenszel test. p < 0.05 was considered statistically significant
CI, confidence interval; rhEPO, recombinant human erythropoietin
*p < 0.05, rhEPO group vs. control group using Fisher exact test;
**p < 0.01, comparing ROP outcomes with gestational age, birth weight using Fisher exact test