Table V.

Multivariable regression of the association between continuous blood marker results and acute readmission.

Variable	TKA				THA
	Development (2011 to 2016)		Validation (2017 to 2018)		Development (2011 to 2016)		Validation (2017 to 2018)
Patients, n	82,810		55,159		46,889		31,643
Readmissions, n (%)	2,635 (3.2)		1,748 (3.2)		1,623 (3.5)		1,102 (3.5)
	OR (95% CI)	p-value	OR (95% CI)	p-value	OR (95% CI)	p-value	OR (95% CI)	p-value
Albumin	0.82 (0.76 to 0.88)	< 0.0001	0.80 (0.73 to 0.88)	< 0.0001	0.82 (0.74 to 0.91)	< 0.0001	0.78 (0.69 to 0.89)	< 0.0001
HCT	0.86 (0.80 to 0.94)	0.0005	0.81 (0.73 to 0.89)	< 0.0001	0.89 (0.80 to 0.99)	0.0258	0.70 (0.62 to 0.89)	< 0.0001
Platelets	0.93 (0.85 to 1.01)	0.0688	0.89 (0.89 to 0.98)	0.0242	1.00 (0.90 to 1.10)	0.9404	0.98 (0.86 to 1.11)	0.7156
WBC	1.13 (1.05 to 1.21)	0.0008	1.14 (1.04 to 1.25)	0.0054	1.09 (1.01 to 1.17)	0.0281	1.18 (1.06 to 1.32)	0.0027
eGFR	0.75 (0.69 to 0.83)	< 0.0001	0.78 (0.71 to 0.87)	< 0.0001	1.00 (0.90 to 1.11)	0.9371	0.96 (0.84 to 1.09)	0.4929
Sodium	0.90 (0.83 to 0.97)	0.0057	0.88 (0.80 to 0.96)	0.0063	0.98 (0.88 to 1.08)	0.6214	0.93 (0.83 to 1.05)	0.2568

Odds ratios are standardized to demonstrate odds adjustment per two standard deviation incremental increase in each variable, allowing for magnitude comparison between variables. Odds ratios are adjusted for the patient and treatment factors listed in Table I – adjusted odds ratios for these variables are presented in Supplementary Material 4. Variables are considered statistically significant if p < 0.0005 is maintained across both development and validation cohorts.

CI, confidence interval; eGFR, estimated glomerular filtration rate; HCT, haematocrit; OR, odds ratio; WBC, white blood cell count.