TABLE 3.

Risk associated pre‐operative Hb thresholds and decision curve analysis results for THA and TKA.

Procedure	Outcome	Risk thresholds (%)	Harm to benefit ratio	Associated Hb cut‐off (g/L)	No. true positives	No. false positives	No. true negatives	No. false negatives	NB per 1000 patients: Hb (g/L) vs. none	NR per 100 patients: Hb (g/L) vs. all
THA	Post‐operative Hb below transfusion trigger (70 g/L)	1	1:99	<116	16	434	4336	7	2.4	76
		0.75	1:133	<118	18	533	4237	5	2.9	74.6
		0.5	1:199	<122	19	817	3953	4	3.2	67.6
		0.25	1:399	<127	20	1334	3436	3	3.5	46.7
		0.1	1:999	<139	23	3003	1767	0	3.9	10.5
	Post‐operative Hb below transfusion trigger (80 g/L)	1	1:99	<136	130	2478	2177	8	22	30.1
		0.75	1:133	<138	132	2755	1900	6	23.2	23.1
		0.5	1:199	<143	135	3393	1262	3	24.7	16.5
		0.25	1:399	<149	137	3950	705	1	26.5	6.4
		0.1	1:999	<164	138	4576	79	0	27.9	5
	Post‐operative blood transfusion a	1	1:99	<153	292	3552	368	9	60.7	−12.4
		0.75	1:133	<156	297	3677	243	4	63.8	−6.8
		0.5	1:199	<162	298	3823	97	3	66.1	−11.6
		0.25	1:399	<169	300	3886	34	1	68.8	−8.6
		0.1	1:999	<185	301	3917	3	0	70.4	0.2
TKA	Post‐operative Hb below transfusion trigger (80 g/L)	1	1:99	<123	29	443	1733	1	11.1	74.1
		0.75	1:133	<125	29	538	1638	1	11.3	68.3
		0.5	1:199	<128	29	681	1495	1	11.6	58.7
		0.25	1:399	<132	29	922	1254	1	12.1	38.8
		0.1	1:999	<143	30	1588	588	0	13	39.1
	Post‐operative blood transfusion a	1	1:99	<144	77	1450	479	6	31.2	−3.5
		0.75	1:133	<147	80	1581	348	3	33.8	−2.4
		0.5	1:199	<152	82	1754	175	1	35.9	−9.7
		0.25	1:399	<159	83	1868	61	0	38.9	3
		0.1	1:999	<177	83	1929	0	0	40.3	0.3

Abbreviations: THA, total hip arthroplasty; TKA, total knee arthroplasty; Hb, haemoglobin; NB, net benefit; NR, net reduction.

^a Blood transfusion based on data from 2013 to 2018.