TABLE 4.

Risk associated pre‐operative Hb thresholds and decision curve analysis results for THA and TKA using data limited to 2015–2018.

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	12	240	2408	2	3.7	84
		0.75	1:133	<117	12	268	2380	2	3.8	79.5
		0.5	1:199	<120	12	359	2289	2	3.8	71.0
		0.25	1:399	<124	12	542	2106	2	4	49.1
		0.1	1:999	<134	13	1261	1387	1	4.5	26.2
	Post‐operative Hb below transfusion trigger (80 g/L)	1	1:99	<131	61	970	1627	4	19.1	45
		0.75	1:133	<133	61	1130	1467	4	19.7	35.2
		0.5	1:199	<137	62	1459	1138	3	20.7	22.9
		0.25	1:399	<141	65	1744	853	0	22.8	32.0
		0.1	1:999	<154	65	2385	212	0	23.6	16.6
	Post‐operative blood transfusion	1	1:99	<146	129	2024	530	11	40.3	−20.8
		0.75	1:133	<149	133	2162	392	7	43.3	−19.8
		0.5	1:199	<154	136	2342	212	4	45.8	−27.8
		0.25	1:399	<161	138	2484	70	2	48.9	−27.0
		0.1	1:999	<179	140	2549	5	0	51.0	0.5
TKA	Post‐operative Hb below transfusion trigger (80 g/L)	1	1:99	<120	8	177	1099	1	5.0	79.1
		0.75	1:133	<121	8	200	1076	1	5.1	73.4
		0.5	1:199	<125	8	304	972	1	5.1	62.0
		0.25	1:399	<128	8	394	882	1	5.5	37.6
		0.1	1:999	<139	9	794	482	0	5.8	−25.5
	Post‐operative blood transfusion	1	1:99	<139	32	786	489	3	18.7	17.5
		0.75	1:133	<142	34	891	384	1	20.8	19.2
		0.5	1:199	<147	34	1033	242	1	22.1	5.4
		0.25	1:399	<154	35	1180	95	0	24.5	7.3
		0.1	1:999	<170	0	3	0	0	25.8	1.3

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