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Aspartate aminotransferase (AST) to platelet ratio index as a predictor of liver fibrosis in chronic hepatitis C

BACKGROUND: The degree of liver fibrosis is the main determinant of clinical outcome of chronic hepatitis C (CHC). Liver histology is considered the gold standard for assessing the degree of liver fibrosis. However, liver biopsy is invasive and costly procedure associated with sampling error, interobserver variability and potential complications. Therefore, there is a need for simple, noninvasive blood test that could serve as a surrogate for biopsy to distinguish mild from significant fibrosis in CHC. Some recent studies have found AST to platelet ratio index (APRI) as an accurate predictor of fibrosis in CHC 1, 2. AIM: The aim of our study was to evaluate clinical efficacy of APRI as a predictor of the degree of liver fibrosis in CHC patients. METHODS: We retrospectively analysed 43 consecutive patients (21 male, 22 female, mean age 38.7 years) with CHC and no history of alcohol abuse, who underwent liver biopsy at the Charity Sisters University Hospital, Zagreb. The liver biopsy specimens were staged blindly by a single pathologist using the Ishak scoring system. Significant (moderate/severe) fibrosis was determined as an Ishak score&#8805; 3. Blood samples were assayed for AST and platelet count. APRI was calculated as AST value/upper limit of normal x 100/platelets. In previous studies of APRI, thresholds of 0.5 or lower were used to indicate mild fibrosis and 1.0 or higher to indicate significant fibrosis 1, 2. Results obtained with APRI were compared with biopsy results. RESULTS: Of 43 patients studied, 30 (69.8%) had no/mild fibrosis (Ishak score<3) and 13 (30.2%) patients had significant fibrosis (Ishak score&#8805; 3). For the prediction of mild fibrosis, when using a previously described cut-off of 0.42, APRI had a sensitivity of 53.9% with a specificity of 84.6%, negative predictive value (NPV) was 44.0% and positive predictive value (PPV) 88.9%. In predicting significant fibrosis, when using a cut-off of 1.0, APRI showed a sensitivity of 54.0% and a specificity of 86.7%, PPV was 63.6% while NPV was 81.2%. But, when using a cut-off of 0.60 for significant fibrosis, NPV was 91.3%. CONCLUSION: This study confirms that the APRI is an accurate index and can be used to differentiate mild from moderate/severe fibrosis in patients with CHC. If APRI is <0.60 there is a 91.3% chance that significant fibrosis does not exist. Application of this simple index alone, or in combination with other blood tests, can decrease the need for more invasive staging of CHC using liver biopsy.

APRI; chronic hepatitis C; liver fibrosis; biopsy

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