Table 5. Stratified Risk (95% Confidence... | American Society of Hematology

Table 5.

Stratified Risk (95% Confidence Interval) of HPA-1a Alloimmunization and its Complications in At-Risk Populations

Population (n)
HPA-1a	NK	Negative	Negative	Negative	Negative	Negative
HLA-DRB3^4-1500101	NK	NK	Positive	NK	Positive	Positive
Anti–HPA-1a	NK	NK	NK	Negative	Positive at any time	Persistently positive antenatally
Event	25,379	387	123	341	46	32
HPA-1a negativity	1:40 (36.7-42.8)
HPA-1a alloimmunization	1:347^4-150(282-451)	1:8.4 (6.9-12.1)	1:2.8 (2.3-3.7)
Thrombocytopenic infant^4-151	1:336^4-150 (250-509)	1:8.6^‡(6.5-12.7)	1:4.9 (3.6-7.6)	1:21^‡ (13.4-46.3)	1:2.1 (1.6-3.0)	1:1.8 (1.4-2.7)
Severe thrombocytopenia^4-153	1:1100^4-150 (684-2910)	1:28^‡ (18-73)	1:15 (9.2-46.6)	1:125^‡ (52.3-∞)	1:5.5 (3.4-14.7)	1:3.9 (2.4-9.6)
Fetal hemorrhage	1:15,400^4-150 (5240-∞)	1:385 (130-∞)	1:123 (41.7-∞)	0	1:44 (15.0-∞)	1:31 (10.6-∞)

Population (n)
HPA-1a	NK	Negative	Negative	Negative	Negative	Negative
HLA-DRB3^4-1500101	NK	NK	Positive	NK	Positive	Positive
Anti–HPA-1a	NK	NK	NK	Negative	Positive at any time	Persistently positive antenatally
Event	25,379	387	123	341	46	32
HPA-1a negativity	1:40 (36.7-42.8)
HPA-1a alloimmunization	1:347^4-150(282-451)	1:8.4 (6.9-12.1)	1:2.8 (2.3-3.7)
Thrombocytopenic infant^4-151	1:336^4-150 (250-509)	1:8.6^‡(6.5-12.7)	1:4.9 (3.6-7.6)	1:21^‡ (13.4-46.3)	1:2.1 (1.6-3.0)	1:1.8 (1.4-2.7)
Severe thrombocytopenia^4-153	1:1100^4-150 (684-2910)	1:28^‡ (18-73)	1:15 (9.2-46.6)	1:125^‡ (52.3-∞)	1:5.5 (3.4-14.7)	1:3.9 (2.4-9.6)
Fetal hemorrhage	1:15,400^4-150 (5240-∞)	1:385 (130-∞)	1:123 (41.7-∞)	0	1:44 (15.0-∞)	1:31 (10.6-∞)

Abbreviation: NK, not known.

Extrapolated from actual observations.

Cord platelet count ≤150 × 10⁹/L.

Based on 284 cord blood platelet counts.

Cord platelet count, <50 × 10⁹/L.