Table 3.

Positive likelihood ratios (LR+) and negative likelihood ratios (LR−) of different cutoff points for SDMA and serum creatinine concentration to detect different categories of %GFR decrease below the mean GFR of the patient's body weight category

Variables	Sample size	LR+ %GFR ↓ ≥20% (95% CI)	LR− %GFR ↓ ≥20% (95% CI)	LR+ %GFR ↓ ≥30% (95% CI)	LR− %GFR ↓ ≥30% (95% CI)	LR+ %GFR ↓ ≥40% (95% CI)	LR− %GFR ↓ ≥40% (95% CI)
SDMA > 10 μg/dL	90	1.2 (1.1‐1.4)	0.2 (0.0‐1.1)	1.2 (1.0‐1.4)	0.3 (0.0‐2.2)	1.1 (0.9‐1.3)	0.6 (0.1‐3.8)
SDMA > 12 μg/dL	90	1.5 (1.1‐1.9)	0.4 (0.2‐0.9)	1.5 (1.1‐1.9)	0.3 (0.1‐1.1)	1.4 (1.1‐1.8)	0.3 (0.0‐1.8)
SDMA > 14 μg/dL	90	1.7 (1.2‐2.4)	0.5 (0.2‐0.9)	1.4 (1.0‐2.1)	0.6 (0.3‐1.2)	1.8 (1.3‐2.4)	0.2 (0.0‐1.3)
SDMA > 16 μg/dL	90	3.0 (1.7‐5.1)	0.5 (0.3‐0.8)	2.4 (1.5‐3.9)	0.5 (0.2‐0.9)	3.1 (2.1‐4.7)	0.1 (0.0‐0.9)
SDMA > 18 μg/dL	90	8.9 (2.8‐28.6)	0.6 (0.4‐0.8)	5.7 (2.5‐12.9)	0.5 (0.3‐0.8)	7.1 (3.6‐14.2)	0.2 (0.1‐0.8)
SDMA > 20 μg/dL	90	5.7 (1.7‐19.6)	0.7 (0.6‐0.9)	7.9 (2.7‐23.6)	0.6 (0.4‐0.9)	8.0 (3.2‐20.1)	0.4 (0.2‐0.9)
Creatinine ≥ 1.0 mg/dL	90	1.8 (1.4‐2.5)	0.3 (0.1‐0.6)	1.6 (1.3‐2.1)	0.2 (0.1‐0.9)	1.6 (1.2‐2.1)	0.2 (0.0‐1.5)
Creatinine ≥ 1.1 mg/dL	90	2.6 (1.7‐3.9)	0.2 (0.1‐0.5)	2.2 (1.6‐3.1)	0.2 (0.1‐0.7)	2.0 (1.5‐2.8)	0.2 (0.0‐1.2)
Creatinine ≥ 1.2 mg/dL	90	3.8 (2.1‐6.8)	0.4 (0.2‐0.6)	3.3 (2.1‐5.2)	0.2 (0.1‐0.6)	3.0 (2.0‐4.5)	0.1 (0.0‐0.9)
Creatinine ≥ 1.3 mg/dL	90	5.4 (2.6‐11.4)	0.4 (0.3‐0.7)	5.0 (2.9‐8.7)	0.2 (0.1‐0.6)	4.0 (2.5‐6.3)	0.1 (0.0‐0.8)
Creatinine ≥ 1.4 mg/dL	90	10.4 (2.5‐44.3)	0.7 (0.5‐0.9)	8.9 (3.1‐25.9)	0.5 (0.3‐0.8)	9.3 (3.9‐22.3)	0.3 (0.1‐0.8)
Creatinine ≥ 1.5 mg/dL	90	—	0.9 (0.8‐1.0)	2.0 (0.2‐20.9)	1.0 (0.9‐1.1)	4.0 (0.4‐40.3)	0.9 (0.8‐1.1)

Notes: The LR+ is the probability of a dog with decreased GFR to have the analyte exceeding cutoff divided by the probability of a dog with normal GFR to have the same analyte exceeding cutoff ($\mathit{LR}+=\frac{\mathit{\text{sensitivity}}}{1-\mathit{\text{specificity}}})$. A LR+ greater than 1 indicates that the test result is associated with decreased GFR. The higher the LR+, the stronger the association. The LR− is the probability of a dog with decreased GFR to have the analyte below the cutoff divided by the probability of a dog with normal GFR to have the same analyte below the cutoff ($\mathit{LR}-=\frac{1-\mathit{\text{sensitivity}}}{\mathit{\text{specificity}}})$. A likelihood ratio less than 1 indicates that the result is associated with absence of the disease. The lower the LR− (trending towards 0), the stronger the exclusion.

Abbreviations: GFR, glomerular filtration rate; SDMA, symmetric dimethylarginine.