Summary

DOI: 10.1373/clinchem.2008.121921

A 64-year-old female with long-standing end-stage renal disease (ESRD),1 status post 2 failed renal transplants, was evaluated for management of renal osteodystrophy with particular concern for adynamic bone disease (ABD). ABD was suspected because of low normal serum intact parathyroid hormone (PTH) concentrations (range 2.5–54 ng/L, reference range 10–65 ng/L), intermittently increased serum calcium concentrations (range 88–107 mg/L, reference range 84–105 mg/L), and severe osteoporosis.



Student Discussion

Student Discussion Document (pdf)

Danni L. Meany,1 Suzanne M. Jan de Beur,2 Mary Jo Bill,1 and Lori J. Sokoll1*

1Department of Pathology; and 2Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD.
* Address correspondence to this author at: Department of Pathology, Johns Hopkins Medical Institutions, 600 N. Wolfe St., Meyer B-125, Baltimore, MD 21287. Fax 410-614-7609; e-mail lsokoll@jhmi.edu.

Case Description

A 64-year-old female with long-standing end-stage renal disease (ESRD), status post 2 failed renal transplants, was evaluated for management of renal osteodystrophy with particular concern for adynamic bone disease (ABD). ABD was suspected because of low normal serum intact parathyroid hormone (PTH) concentrations (range 2.5–54 ng/L, reference range 10–65 ng/L), intermittently increased serum calcium concentrations (range 88–107 mg/L, reference range 84–105 mg/L), and severe osteoporosis. However, her mildly increased serum alkaline phosphatase activities (range 149–196 U/L, reference range 30–120 U/L) were inconsistent with the low bone turnover observed in ABD. This discrepant clinical profile prompted investigation into the PTH assay used at our institution. Simultaneous samples were analyzed for intact PTH on our Roche Elecsys 2010 immunoassay analyzer and at a reference laboratory (Quest Diagnostics) on the Siemens Immulite 2000 immunoassay analyzer. Discrepant values of 48 and 786 ng/L were obtained, respectively.

Questions to Consider

  • What are the roles of PTH in calcium and bone metabolism?
  • What are potential explanations for immunoassay results that do not correlate with the clinical picture?
  • What approaches can be used to investigate potential immunoassay interferences?

Final Publication and Comments

The final published version with discussion and comments from the experts appears in the September 2009 issue of Clinical Chemistry, approximately 3-4 weeks after the Student Discussion is posted.

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DOI: 10.1373/clinchem.2008.121921
Copyright © 2009 American Association for Clinical Chemistry