Table III.

Univariable association of continuous blood marker results with acute readmission in development and validation.

TKA					THA
Variable	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	0.69 (0.64 to 0.74)	< 0.0001	0.64 (0.59 to 0.70)	< 0.0001	0.64 (0.58 to 0.70)	< 0.0001	0.55 (0.49 to 0.61)	< 0.001
HCT	0.79 (0.73 to 0.85)	< 0.0001	0.70 (0.64 to 0.77)	< 0.0001	0.75 (0.69 to 0.83)	< 0.0001	0.56 (0.50 to 0.62)	< 0.0001
Platelets	0.84 (0.77 to 0.91)	< 0.0001	0.81 (0.73 to 0.89)	< 0.0001	0.98 (0.89 to 1.08)	0.6835	0.98 (0.87 to 1.10)	0.6927
WBC	1.20 (1.13 to 1.28)	< 0.0001	1.22 (1.12 to 1.32)	< 0.0001	1.19 (1.11 to 1.29)	< 0.0001	1.33 (1.21 to 1.46)	< 0.0001
eGFR	0.62 (0.56 to 0.67)	< 0.0001	0.60 (0.54 to 0.66)	< 0.0001	0.81 (0.72 to 0.90)	< 0.0001	0.65 (0.57 to 0.74)	< 0.0001
Sodium	0.86 (0.80 to 0.93)	< 0.0001	0.83 (0.76 to 0.91)	< 0.0001	0.91 (0.82 to 1.00)	0.0502	0.84 (0.75 to 0.94)	0.0032

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 unadjusted. 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; THA, total hip arthroplasty; TKA, total knee arthroplasty; WBC, white blood cell count.