Determining both the concentration of serum procollagen III peptide (PIIIP) and the PGA index (PT, GGT, apolipoprotein A1) may help identify patients with liver disease who are developing fibrosis and cirrhosis. Serum PIIIP correlates with activity of the fibrogenic process, while the serum apolipoprotein A1 decreases as fibrosis progresses.
NOTE: An alternative form of the PGA is given in PGA Index of Poynard et al for Identifying Alcoholic Liver Disease based on the prothrombin time value rather than the INR.
Parameters in the PGA score:
(1) prothrombin time (PT), expressed as the INR (International Normalized Ratio)
(2) serum GGT
(3) serum apolipoprotein A1 (apoA1)
|
Parameter |
Finding |
Points |
|
INR |
< 1.25 |
0 |
|
|
1.25 – 1.41 |
1 |
|
|
1.42 – 1.65 |
2 |
|
|
1.66 – 1.99 |
3 |
|
|
>= 2.00 |
4 |
|
serum GGT |
< 20 IU/mL |
0 |
|
|
20 – 49 IU/mL (1.01 - 2.49 times ULN) |
1 |
|
|
50 – 99 IU/mL (2.5-4.9 times ULN) |
2 |
|
|
100 – 199 IU/mL (5-9.9 times ULN) |
3 |
|
|
>= 200 IU/mL (>= 10 times ULN) |
4 |
|
serum apolipoprotein A1 |
>= 200 g/L |
0 |
|
|
175 – 199 g/L (0.88 to 0.99 times LLN) |
1 |
|
|
150 – 174 g/L (0.75 to 0.87 times LLN) |
2 |
|
|
125 – 149 g/L (0.63 to 0.74 times LLN) |
3 |
|
|
< 125 g/L (< 0.63 times LLN) |
4 |
where:
• The serum apolipoprotein A1 was measured by nepheloturbidometry using an assay by Immuno (Sevenoaks, UK).
• The reference ranges for the normal population are not stated, but these appears to match the values with the 0 point assignments.
• Procollagen III peptide was measured with an assay by Behring (Marburg, Germany).
NOTES on units:
(1)The values for GGT in the paper are given in IU/mL, but the values match the range given in Tietz's Clinical Guide to Laboratory Tests in IU/L. I will assign points in the implementation as multiples of the upper limit of normal, assuming < 20 is the ULN.
(2) Tietz lists the normal apolipoprotein level as 1.0 to 1.5 g/L (100 – 150 mg/dL). I will assign points in the implementation as multiples of the lower limit of normal, assuming 200 is the LLN.
PGA index =
= (points for the PT as INR) + (points for the serum GGT) + (points for serum apoA1)
Interpretation:
• minimum PGA index: 0
• maximum PGA index: 12
• The control group had a serum PIIIP concentration of 0.34 – 0.46 U/mL.
• A cutoff for the PGA index > 3 was 91% sensitive and 81% specific for fibrosis or cirrhosis (positive predictive value 84.5%, negative predictive value 89%).
• A cutoff for the PIIIP > 0.7 U/mL was 94% sensitive and 81% specific for fibrosis or cirrhosis (positive predictive value 85%, negative predictive value 92%).
• If both tests exceeded the cutoffs, the tests were 85% sensitive and 93% specific for fibrosis or cirrhosis (positive predictive value 93%, negative predictive value 85%).
• If only 1 of the 2 tests exceeded its cutoff, the tests were 98.5% sensitive and 70% specific for fibrosis or cirrhosis (positive predictive value 78%, negative predictive value 98%).
Purpose: To use the PGA index and procollagen III peptide concentration to identify a patient with liver disease who has developed hepatic fibrosis and/or cirrhosis.
Specialty: Gastroenterology
Objective: severity, prognosis, stage
ICD-10: K70.3, K71.7, K74,
