title: High Uric Acid (UA) Negatively Affects Serum Tartrate-Resistant Acid Phosphatase 5b (TRACP 5b) Immunoassay.
abstract: BACKGROUND
  Bone metastases often occur in the majority of patients with advanced cancer, such as prostate cancer, lung cancer and breast cancer. Serum tartrate-resistant acid phosphatase 5b (TRACP 5b), a novel bone resorption marker, has been used gradually in the clinics as a specific and sensitive marker of bone resorption for the early diagnosis of cancer patients with bone metastasis. Here, we reported that high concentrations of uric acid (UA) lead to decrease of TRACP 5b levels and determined whether TRACP 5b level was associated with UA in interference experiment.
  
  
  METHODS
  A total of 77 patients with high concentrations of UA and 77 healthy subjects were tested to evaluate the differences in their TRACP 5b levels. Serial dilutions of UA were respectively spiked with a known concentration of TRACP 5b standard sample, then Serum TRACP 5b was detected by using bone TRAP® Assay. A correction equation was set to eliminate UA-derived TRACP 5b false-decrease. The effect of this correction was evaluated in high-UA individuals.
  
  
  RESULTS
  The average TRACP level of the high-UA individuals (1.47 ± 0.62 U/L) was significantly lower than that of the healthy subjects (2.62 ± 0.63 U/L) (t-test, p < 0.0001). The UA correction equation derived: ΔTRACP 5b = -1.9751lgΔUA + 3.7365 with an R2 = 0.98899. Application of the UA correction equation resulted in a statistically non-significant difference in TRACP 5b values between the healthy subjects and high-UA individuals (p = 0.24).
  
  
  CONCLUSIONS
  High UA concentrations can falsely decrease TRACP 5b levels due to a method-related systematic error. To avoid misdiagnoses or inappropriate therapeutic decisions, increased attention should be paid to UA interference, when TRACP 5b is used for early diagnosis of cancer patients with bone metastasis, evaluation of the aggressiveness of osteosarcoma or prediction of survival in prostate cancer and breast cancer with bone metastases.
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Zhi-Qi
authors.initials: ZQ
authors.lastname: Wu
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Erfu
authors.initials: E
authors.lastname: Xie
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Wei-Juan
authors.initials: WJ
authors.lastname: Song
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Rui-Xia
authors.initials: RX
authors.lastname: Yang
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Cheng-Jing
authors.initials: CJ
authors.lastname: Yan
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Bing-Feng
authors.initials: BF
authors.lastname: Zhang
authors.affiliation: Department of Laboratory Medicine, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Hua-Guo
authors.initials: HG
authors.lastname: Xu
mesh_terms: D000135:Acid Phosphatase / Q000097:blood*; D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D001859:Bone Neoplasms / Q000097:blood; D001862:Bone Resorption / Q000097:blood; D016022:Case-Control Studies; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay; D007527:Isoenzymes / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000097:blood / Q000175:diagnosis; D000071681:Tartrate-Resistant Acid Phosphatase; D014527:Uric Acid / Q000097:blood*; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D007527:Isoenzymes; D014527:Uric Acid; C000605510:ACP5 protein, human; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase