Table 1.

Sensitivity (Se), specificity (Sp), 95% confidence interval (CI), positive predictive value (PPV), and negative predictive value (NPV) for diagnosing subclinical ketosis using milk fat-to-protein ratio (FPR) with a cut-off of > 1.42 as the test under evaluation and blood concentration of beta-hydroxybutyrate (BHBA) with a cut-off of ≥ 1.2 mmol/L as the reference test

	BHBA ≥ 1.2 mmol/L (n = 24)	BHBA < 1.2 mmol/L (n = 134)
FPR > 1.42 (n = 69)	22	47	PPV = 32% (22/69)
FPR ≤ 1.42 (n = 89)	2	87	NPV = 98% (87/89)
	Se = 92% (22/24)	Sp = 65% (87/134)
	95% CI = 73% to 99%	95% CI = 56% to 73%