title: Switching between parathormone (PTH) assays: the impact on the diagnosis of renal osteodystrophy.
abstract: BACKGROUND
  Clinical guidelines for decision-making in chronic kidney disease (CKD) consider parathormone (PTH) levels. The measured PTH values differ if novel full length PTH(1-84) assays are used instead of earlier intact iPTH assays. In this study we analyzed how the classification of CKD patients alters when iPTH assays are switched to PTH(1-84) assays.
  
  
  METHODS
  Plasma samples were collected prior to dialysis sessions from 110 consecutive CKD patients on maintenance hemodialysis. PTH levels were determined with iPTH assays (Elecsys, Architect and DiaSorin Liaison N-tact) and PTH(1-84) assays (Elecsys and Liaison). Using KDIGO guidelines patients were classified as being below, above and in the recommended target range (RTR) of PTH. The results of classification with different assays were evaluated and, a novel calculation method of RTR was implemented.
  
  
  RESULTS
  The prevalence of patients with PTH in RTR is comparable with each assay, but the individual patients differed. PTH(1-84) Elecsys and Liaison assays classified more patients as being below RTR than iPTH Elecsys and Architect but not Liaison N-tact assay (27.3%, 22.7% vs. 41%, 31.8%, and 36.4%, respectively). In turn, PTH(1-84) Elecsys and Liaison assays identified less CKD patients with PTH above the RTR than iPTH except N-tact assays (6.4%, 10% vs. 16.3%, 19%, and 6.3%, respectively). Using our calculation method, our discrimination values for PTH(1-84) assays to achieve classification identical to that with iPTH Elecsys were lower than those recommended by the manufacturer.
  
  
  CONCLUSIONS
  Current guidelines for the treatment of secondary hyperparathyroidism in CKD should consider the type of assays used for PTH measurement. Each laboratory should assess its own RTR for PTH tests to achieve comparable classification. The presented calculation is simple, it mimics an everyday situation, switching from one assay to another one, and provides useful RTR values for PTH tests.
authors.affiliation: Department of Laboratory Medicine Institute, Semmelweis University, Budapest, Hungary.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Bekő
authors.forename: Henriett
authors.initials: H
authors.lastname: Butz
authors.forename: Klára
authors.initials: K
authors.lastname: Berta
authors.forename: András
authors.initials: A
authors.lastname: Tislér
authors.forename: Ferenc
authors.initials: F
authors.lastname: Olajos
authors.forename: Barna
authors.initials: B
authors.lastname: Vásárhelyi
authors.forename: Attila
authors.initials: A
authors.lastname: Patócs
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000097:blood / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D017410:Practice Guidelines as Topic; D055815:Young Adult
chemical_list: D010281:Parathyroid Hormone