99m Tc-HEPIDA hepatic clearance as a diagnostic tool: usefulness of a single sample plasma and hepatic clearance of 99m Tc-HEPIDA for assessment of hepatic parenchyma performance

Abstract

BACKGROUND: A simplified method of ^99mTc-HEPIDA clearance determination, both plasma and hepatic, depends upon measuring the radiopharmaceutical concentration in plasma of a blood sample taken once in the time range from 68-83 min after injection of compound, and measurement of activity voided (excreted) with urine about five minutes after blood sampling. The aim of the present study was to analyze the clinical usefulness of both clearances, as determined by the simplified method in view of the diagnostic usefulness of both clearances (particularly of hepatic clearance) as determined by the respective multisampling method.
MATERIAL AND METHODS: For the analysis, archived data of studies in 134 individuals (48 healthy individuals and 86 patients with chronic liver parenchyma damage) were used, in which plasma clearance (Cl_Pl) and hepatic clearance (Cl_Hp) ^99mTc -HEPIDA were determined by the standard multisample method - the values of such determined clearances constituted clearance referential values for further comparative analyses. The clearances Cl_Pl and Cl_Hp were determined by the simplified method separately for three blood sampling times of: 60, 75 and 90 min, using the same archived data for calculation of corresponding concentrations of ^99mTc-HEPIDA in plasma. For urinary clearances - which were necessary for calculation of Cl_Hp - archived data were utilized on activity contained in voided urine (at about 95 min.). The clinical reference system used here was the semi-quantitative assessment of liver function, performed on the basis of commonly used basic biochemical indices (AST, ALT, GGTP, bilirubin, albumin and gammaglobulin in serum, proteinogram and prothrombin index). For each test there were 4 categories of results (sub-ranges) selected, which were ranked from 0 to 3. For each patient the ranks for the results of each test were summed, giving a total sum (called SP). These latter sums of ranks served as a reference system, characterizing liver condition (performance) in each individual.
RESULTS: Clearance, Cl_Pl and Cl_Hp, values, obtained by a simplified method, were correlated with respective values determined by the multisampling method, and with ranks (SP) representing classification of degree of hepatic parenchyma damage - SP. On the basis of the attribute independence Χ² test, the coherence of clearances (simplified determination) with SP was assessed. Also, analysis of variance of SP-values and clearance was performed using Spearman’s theory for testing the correlation of non-continuous variables. By factorial analysis a factor responsible for changes in individual quantities (results of biochemical tests and ^99mTc-HEPIDA clearances) was computed. Its loading was determined for each individual quantity. During analysis for each moment of blood sampling tight correlations of clearance values, obtained by the simplified method, were determined with referential values. The closest correlation was obtained for blood sampling at 75 min. It was found that there are negative correlations between values of hepatic and plasmatic clearances and SP. The values of r obtained for Cl_Hp are close to those obtained for analogical correlations by multisampling methods. However, the values of correlation coefficient obtained for Cl_Pl by single sample method are greater than those for Cl_Pl determined by multisampling method.
CONCLUSIONS: Factor loading, known as “liver incapacity”, is greater for Cl_Hp determined by single sample method, but lower than comparable hepatic clearance loading determined by the multi-sample procedure. Values of incapacity factor for Cl_Pl are lower than for Cl_Hp, but the lowest value was obtained for Cl_Pl determined by the multisampling method. Obtained values Χ², r and loading of incapacity factor speak in favour of the correlations between the degree of hepatic parenchyma performance and the values of clearances determined by the simplified method. However, this correlation is closer for Cl_Hp than for Cl_Pl. In view of such a distinct correlation, there is good justification for the implementation of the simplified method for the determination of hepatic clearances used in diagnostic analysis of hepatic performance.