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
Background 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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Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, SwedenUniv Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Carling, T
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Szabo, E
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Szabo, E
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Bai, M
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Bai, M
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Ridefelt, P
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Ridefelt, P
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Westin, G
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Westin, G
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Gustavsson, P
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Gustavsson, P
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Trivedi, S
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Trivedi, S
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Hellman, P
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Hellman, P
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Brown, EM
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Brown, EM
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Dahl, N
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Dahl, N
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Rastad, J
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
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Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, SwedenUniv Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Carling, T
;
Szabo, E
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h-index: 0
机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Szabo, E
;
Bai, M
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h-index: 0
机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Bai, M
;
Ridefelt, P
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h-index: 0
机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Ridefelt, P
;
Westin, G
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Westin, G
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Gustavsson, P
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Gustavsson, P
;
Trivedi, S
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Trivedi, S
;
Hellman, P
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Hellman, P
;
Brown, EM
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Brown, EM
;
Dahl, N
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden
Dahl, N
;
Rastad, J
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机构:Univ Uppsala Hosp, Dept Surg, Endocrine Surg Unit, S-75185 Uppsala, Sweden