A comparison between des‐γ‐carboxy prothrombin and α‐fetoprotein as markers of hepatocellular carcinoma in southern African Blacks

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Abstract
Des‐γ‐carboxy prothrombin (DCP), a precursor of prothrombin, has been reported recently to be as good a marker, or even better, of hepatocellular carcinoma than α‐fetoprotein (α‐FP). The sensitivity, specificity and predictive values of the two markers have been compared in 98 southern African Blacks with hepatocellular carcinoma and in 120 Black controls with various diseases which might be mistaken clinically for this tumour: 32 with hepatic metastases, 33 with amoebic hepatic abscesses, and 55 with chronic hepatic parenchymal disease. DCP levels were measured using a chromogenic assay with Dispholidus typus venom and staphylocoagulase. The agreement between the two methods was excellent (r= 0.995). α‐FP concentrations were measured by radioimmunoassay. DCP levels were raised in 66 of 98 patients (67.3%) and α‐FP levels in 82 of 98 patients (83.7%) with hepatocellular carcinoma (P= 0.006). The specificity of DCP was also less than that of α‐FP, although the difference just failed to reach statistical significance (P= 0.085). The predictive values of both a positive and a negative test for DCP were significantly less than those for α‐FP (P= 0.047 and 0.048, respectively). When, in an attempt to eliminate false positive results, the diagnostic cut‐off level for DCP was increased from 1.5 to 5.0 mu/ml and that of α‐FP from 20 to 400 ng/ml, the differences between the two markers remained the same. If the two tests were used together, the number of false negative α‐FP results was reduced from 16.3% to 7.1% and the number of equivocal α‐FP results was reduced from 11.2% to 5.1%. It is concluded that DCP is less useful than α‐FP as a single marker of hepatocellular carcinoma in southern African Blacks. However, the two markers can be used together profitably.