title: Comparison between a second and a third generation parathyroid hormone assay in hemodialysis patients.
abstract: OBJECTIVE
  Third generation parathyroid hormone (PTH) assays are new generation assays that do not recognize the PTH7-84 fragment whereas second generation assays detect both PTH1-84 and PTH7-84 fragments. Despite the excellent correlation between both assays in chronic renal failure (CRF) subjects, the mean PTH levels are typically 50% lower with the third compared to the second generation assays. The assessment of third generation PTH assays has not been extensively studied in hemodialysis subjects. The purpose of our study was to compare a third generation PTH assay to a second generation one in a population of hemodialysis subjects.
  
  
  METHODS
  92 haemodialysis subjects (36 women and 56 men) with a mean age of 67±12.9 years were included in this study. Anthropometric and clinical parameters (Body Mass Index (BMI) and blood pressure) were measured. Second and third generation PTH assays (Cis biomedical and Diasorin respectively) were performed in each subject. In addition, the following biochemical tests were measured: 25-hydroxyvitamin D (25-(OH)D), 1,25-hydroxyvitamin D (1,25-(OH)2D), crosslaps and alkaline phosphatase.
  
  
  RESULTS
  The mean second and third generation PTHs are respectively 211±205 pg/ml and 151±164 pg/ml. The mean third generation PTH values are 28.4% lower compared to the second generation ones. Both methods are strongly correlated (r=0.923, p<0.001). This correlation persisted without any significant difference after controlling for gender, age, BMI and Blood Pressure. However, the difference between both methods increases when baseline PTH increases. Each of the second and third generation method is significantly correlated with hemodialysis duration (p<0.01), crosslaps (p<0.001), alkaline phosphatase (p<0.05), but not with age, BMI, Blood Pressure, 25-(OH)D or 1,25-(OH) 2D levels.
  
  
  CONCLUSIONS
  Our results show that both second and third generation PTH methods are strongly correlated in hemodialysis patients mainly when PTH values are low. However, the difference between both methods increases when PTH values are high. More research is needed to establish which method is the gold standard when PTH values are high.
authors.affiliation: Department of Endocrinology, Saint-Joseph University, Beirut, Lebanon. Electronic address: mhcyared@terra.net.lb.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Gannagé-Yared
authors.forename: Chirine
authors.initials: C
authors.lastname: Farès
authors.forename: Tony
authors.initials: T
authors.lastname: Ibrahim
authors.forename: Zeina Abou
authors.initials: ZA
authors.lastname: Rahal
authors.forename: Michele
authors.initials: M
authors.lastname: Elias
authors.forename: Dania
authors.initials: D
authors.lastname: Chelala
mesh_terms: D000368:Aged; D000469:Alkaline Phosphatase / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D015992:Body Mass Index; D001851:Bone Diseases, Metabolic / Q000097:blood; D003094:Collagen / Q000097:blood; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000503:physiopathology / Q000628:therapy; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood; D006435:Renal Dialysis; D013223:Statistics as Topic; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; C110762:glutamyl-lysyl-alanyl-histidyl-aspartyl-glycyl-glycyl-arginine; D014807:Vitamin D; D003094:Collagen; C104450:25-hydroxyvitamin D; D000469:Alkaline Phosphatase
keywords: 1,25-(OH)(2)D; 1,25-hydroxyvitamin D; 25-(OH)D; 25-hydroxyvitamin D; BMI; Body Mass Index; CKD; CRF; Chronic Kidney Disease; Chronic renal failure; Hemodialysis; PTH; Parathyroid hormone; Second; Third generation