Significance of the LP-X test in differential diagnosis of jaundice.

In recent years it has been well documented that the characteristic increase in plasma lipoproteins in patients with obstructive jaundice is the result of the presence of a low-density lipoprotein (relative density 1.006-1.063 g/ml) of abnormal composition and properties. This abnormal lipoprotein has been designated “LP-X.” The development of a simple immunologic test system for determining LP-X provides the basis for a new clinical chemical test that is of use in the differential diagnosis of jaundice. In this study, 2680 LP-X determinations were performed on 1481 subjects: 1309 patients with or without liver disease, and 172 healthy volunteers. Statistical analysis of this series revealed a power of 0.99 and a specifity of 0.98 to demonstrate or exclude cholestasis. In this regard the new test is superior to other blood-chemical assessments. It was never positive in patients without liver disease. However, the LP-X test alone is not adequate to distinguish between intrahepatic cholestasis and extrahepatic biliary obstruction.