Discriminative power of three indices of renal calcium excretion for the distinction between familial hypocalciuric hypercalcaemia and primary hyperparathyroidism: a follow‐up study on methods

Clinical Endocrinology - Tập 69 Số 5 - Trang 713-720 - 2008
Signe Engkjær Christensen1, Peter H. Nissen2, Peter Vestergaard1, Lene Heickendorff2, Kim Brixen3, Leif Mosekilde1
1Departments of Endocrinology and Metabolism C and
2Clinical Biochemistry, Aarhus University Hospital, Aarhus and
3Department of Endocrinology, Odense University Hospital, Odense, Denmark

Tóm tắt

SummaryBackground  Familial hypocalciuric hypercalcaemia (FHH) must be differentiated from primary hyperparathyroidism (PHPT) because prognosis and treatment differ. In daily practice this discrimination is often based on the renal calcium excretion or the calcium/creatinine clearance ratio (CCCR). However, the diagnostic performance of these variables is poorly documented.Aim  To appraise the power of various simple biochemical variables to differentiate between FHH and PHPT using calcium sensing receptor (CASR) gene analysis and histopathological findings as gold standards.Design  Follow‐up approach (direct design).Materials  We included 54 FHH patients (17 males and 37 females, aged 18–75 years) with clinically significant mutations in the CASR gene and 97 hypercalcaemic patients with histologically verified PHPT (17 males and 80 females, aged 19–86 years). All PHPT patients became normocalcaemic following successful neck exploration.Results  Based on receiver operating characteristic (ROC) curve analysis, the CCCR was only marginally better, as judged by the area under curve (AUC = 0·923 ± 0·021 (SE)), than the 24‐h calcium/creatinine excretion ratio (AUC = 0·903 ± 0·027) and the 24‐h calcium excretion (AUC = 0·876 ± 0·029). However, overlap performance analysis disclosed that the CCCR included fewer patients with PHPT together with the FHH patients than the other two variables at different cut‐off points. Based on the ROC curve, the optimal cut‐off point for diagnosing FHH using CCCR was < 0·0115, which yielded a diagnostic specificity of 0·88 and a sensitivity of 0·80. Overlap analysis revealed that a cut‐off point for CCCR at < 0·020 would sample 98% (53/54) of all patients with FHH and include 35% (34/97) of the PHPT patients.Conclusion  Our results support the use of the CCCR as an initial screening test for FHH. We suggest a two‐step diagnostic procedure, where the first step is based on the CCCR with a cut‐off at < 0·020, and the second step is CASR gene analysis in patients with FHH or PHPT.

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Clinical Endocrinology

Tập 69 Số 5

713-720

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