High Bilirubin Levels Interfere with Serum Tartrate-Resistant Acid Phosphatase Determination: Relevance as a Marker of Bone Resorption in Jaundiced Patients

Abstract

Serum tartrate-resistant acid phosphatase (TRAcP) activity is considered to be a biochemical marker of bone resorption. Recently, a lack of specificity of collagen-related markers for assessing bone turnover has been observed in patients with chronic liver disease. Thus, it could be of great interest to determine serum TRAcP activity in such patients. However, nonspecificity of the analytical reaction could occur when hemolyzed, lipemic, or icteric specimens are analyzed. Therefore, we have studied the interference caused by bilirubin in the measurement of serum TRAcP activity using the Hillmann method. The interference was assessed in two pools of serum containing different bilirubin concentrations but with similar total AcP levels. Mixing proportional parts of the two pools, 10 samples were also obtained. Serum activities of total AcP and TRAcP, and the concentration of bilirubin were measured in the 10 samples. Both the actual and the expected values obtained by theoretical calculations were compared. Serum bilirubin values of 2.4 mg/dl showed a negative interference of 15% in the determination of serum TRAcP activity, whereas values of bilirubin higher than 10 mg/dl interfered totally with the measurement of serum TRAcP. Bilirubin did not interfere with the total AcP determination. This study clearly shows the interference of bilirubin in the determination of serum TRAcP. This finding should be considered when bone metabolism disorders are evaluated in jaundiced patients.

Tartrate-Resistant Acid Phosphatase 5b: A Novel Serum Marker of Bone Resorption

“…Several TRAP immunoassays and enzymatic assays have been published, (12)(13)(14)(15)(16)(17)(18)(19) but none of them can distinguish between the osteoclast-derived isoform 5b and the nonosteoclast-derived isoform 5a. The novel TRAP 5b assay we describe here uses MAb O1A to capture TRAP from serum.…”

“…(12,13) However, enzymatic assays are not specific because serum contains other, completely different TRAP enzymes derived from erythrocytes and platelets and because bilirubin interferes with the spectrophotometric detection of the end product of para-nitrophenyl phosphate (pNPP) hydrolysis. (14) These problems can be overcome by using immunoassays utilizing antibodies specific for TRAP. Several immunoassays for TRAP have been published earlier, (15)(16)(17)(18)(19) but no convincing evidence for the usability of serum TRAP as a resorption marker has been obtained.…”

“…Several enzymatic assays measuring serum TRAP activity have been published (12, 13) . However, enzymatic assays are not specific because serum contains other, completely different TRAP enzymes derived from erythrocytes and platelets and because bilirubin interferes with the spectrophotometric detection of the end product of para‐nitrophenyl phosphate (pNPP) hydrolysis (14) . These problems can be overcome by using immunoassays utilizing antibodies specific for TRAP.…”

Molecular Markers of Bone Turnover: Biochemical, Technical and Analytical Aspects

“…This can be achieved by the addition of citrate buffer to the sample [164±167]. In jaundiced patients, high bilirubin levels can interfere with the measurement of serum tartrate-resistant acid phosphatase [168].…”

Characterization of Four Monoclonal Antibodies to Recombinant Human Tartrate-Resistant Acid Phosphatase

“…(5)(6)(7)(8) Serum TRAP has been suggested to be a useful marker of bone resorption, (9,10) and histochemical studies confirm that TRAP is primarily localized in osteoclasts and is secreted during bone resorption. (11,12) Serum TRAP activity is reported to be proportionally increased in patients with increased bone resorption.…”