Table 4.

Positive (PPV) and negative predictive values (NPV) of the simple traffic light grading for any fibrosis or cirrhosis in the model development cohort^a

Setting	Parameter	Predictive value	Fibrosis	Cirrhosis
STL		Simple TL
Hospital setting prior probability: cirrhosis 39%, fibrosis 82%	Red	PPV	0.96	0.69
	Red/amber	PPV	0.88	0.46
	Green	NPV	0.50	0.97
Low prevalence community prior probability: cirrhosis 4%, fibrosis 8%	Red	Est PPV	0.31	0.13
	Red/amber	Est PPV	0.12	0.05
	Green	Est NPV	0.98	1.00
Higher prevalence community prior probability: cirrhosis 10%, fibrosis 20%	Red	Est PPV	0.57	0.27
	Red/amber	Est PPV	0.29	0.13
	Green	Est NPV	0.95	0.99
mSTL		Modified TL
Hospital setting prior probability: cirrhosis 39%, fibrosis 82%	Red	PPV	0.99	0.73
	Red/amber	PPV	0.91	0.48
	Green	NPV	0.59	0.99
Low prevalence community prior probability: cirrhosis 4%, fibrosis 8%	Red	Est PPV	0.63	0.15
	Red/amber	Est PPV	0.17	0.04
	Green	Est NPV	0.99	1.00
Higher prevalence community prior probability: cirrhosis 10%, fibrosis 20%	Red	Est PPV	0.84	0.31
	Red/amber	Est PPV	0.38	0.13
	Green	Est NPV	0.96	1.00

^aAs the prevalence of fibrosis/cirrhosis in a primary care population with suspected liver disease was not known, estimated PPV (Est PPV) and NPV (Est NPV) values were calculated for a range of prevalences: fibrosis (8–20%) and cirrhosis (4–10%). These ranges of risk might be expected in patients with harmful alcohol consumption or known fatty liver and steatohepatitis.