AFP-L3% Test
AFP-L3% - The Test
AFP is a glycoprotein with one complex carbohydrate chain per molecule. Using affinity electrophoresis with the lectin Lens culinaris agglutinin (LCA), AFP can be fractionated into the three variants L1, L2 and L3. AFP-L1 with the lowest affinity for LCA is the most prevalent fraction in patients with non-malignant liver diseases like chronic hepatitis or liver cirrhosis. AFP-L3 has an additional α 1-6 fucose residue attached at the reducing end of N-acetylglucosamine. The high affinity to LCA is based in this modification.
Schematic structure of AFP-L3%
AFP-L3% is the ratio of AFP-L3 to total AFP as percentage. In Japan AFP-L3% has been routinely used for many years as tumor marker for HCC. Since a few years AFP-L3% is FDA cleared in the USA for the risk assessment of HCC and CE-marked for the European market. Recently a novel high sensitive automated immunoassay for AFP-L3 has been developed. In a first study using this improved technique 295 HCC patients and 350 patients with chronic hepatitis and cirrhosis of various aetiologies have been investigated (Tamura et al. Dig Dis Sci 2010). As can be seen in the table below in this study AFP-L3 showed a good sensitivity combined with a high specificity at a cut-off level of 7%.
| Diagnostic parameters of AFP-L3% versus AFP (Tamura et al. 2010) |
||
| AFP-L3% | AFP | |
| Cut-off | 7% | 200 ng/ml |
| Sensitivity | 60% | 34% |
| Specificity | 90% | 98% |
| Positive predictive value | 84% | 93% |
| Negative predictive value | 73% | 64% |
In this study the sensitivity of AFP-L3% was in particular good (41%) in HCC patients with lower AFP concentrations (<20 ng/ml). Thus AFP-L3% could be a powerful tool for detection of HCC at an early stage resulting in the opportunity for curative treatment and improved survival of patients with HCC.
Elevated AFP-L3% values before and after therapy of HCC were compared with the survival time and recurrence rate in many investigations. For example Okuda et al. published in 1999 in the International Journal of Oncology the observation of a significantly improved survival time and a lower recurrence rate in cases of negative AFP-L3% values after treatments of 130 patients mostly with resection (see figure below).
Recurrence rate and survival time against AFP-L3% value before treatment
Another study by Aoyagi et al. in 1998 with 112 HCC patients revealed that the Fucosylation Index (equivalent to AFP-L3%) determined before treatment represents an independent prognostic factor. The authors therefore discussed the selection of therapy depending on the results of the Fucosylation Index.
Elevated AFP-L3% values indicate tumors with increased malignant potential. An investigation by Kusaba et al. compared AFP-L3% values from sera of 48 patients with pathological findings of subsequently resected tumor tissues. Samples from AFP-L3% positive patients stained significantly more with Ki67 antibodies suggesting an increased proliferation rate. Furthermore a decreased staining with α-catenin was interpreted to correlate with distant metastasis.
To find a summarised presentation of AFP-L3%, click here for the general flyer.
To find more technical information about analytical technique, click here to visit the µTASWakoTM i30 page.
AFP-L3% - Ordering
For information concerning cost of AFP-L3% assay including related instrumentation and required material please contact Wako Chemicals GmbH at ++49/2131/311-176, or through e-mail at diagnostika@wako-chemicals.de.