Screening for primary hyperparathyroidism (PHPT) in clinic patients: differential diagnosis between PHPT and malignancy-associated hypercalcemia by routine blood tests

Screening for primary hyperparathyroidism (PHPT) by measurement of the seru m calcium concentration detects one patient per 500-1000 individuals in Wes tern countries, and one patient per 2500-5000 subjects in Japan. Among clin ic patients, however, the presence of many false-positive cases due to mali gnancy-associated hypercalcemia (MAH) reduces the benefit of such screening . We evaluated a new method of screening for PHPT based on the results of r outine blood tests using the hospital information system (HIS) at our hospi tal. This new method could distinguish PHPT from MAH. This study included 2 5 179 blood samples in which the serum calcium (Ca), albumin (Alb), chlorid e (Cl) and inorganic phosphate (IP) concentrations had been measured betwee n March, 1994 and February, 1995 at Osaka University Medical Hospital. The HIS was programmed to pick blood samples that satisfied Formula l [Ca(mEq/m l)>0.3 X Alb(g/dl)+4.1] and Formula 2 {[Cl(mEq/ml)-84] X [10XAlb-15] divide d by [IP(mg/dl) divided by 3.1]>400}, Of data from 25 179 blood samples col lected, those from 54 patients satisfied both Formulae I and 2, The patient s from which these samples were derived from were subject to further analys is: medical records were studied and the intact-parathyroid hormone concent ration was measured if necessary. Of these 54 cases, 19 patients (35.2%) we re subsequently diagnosed with PHPT, including two, who were newly diagnose d with PHPT by this screening procedure. Although 35 (64.8%) of 54 patients were false-positive, many of them were treated with blood purification the rapies in the Department of Pediatrics or the Intensive Care Unit (ICU). On the other hand, there were four false-positive cases (7.4%) caused by MAH. False-negative case in this study was only one patient (5%), whose diagnos is was normocalcemic PHPT, When omitting samples from pediatric patients an d those in ICU, this screening procedure for PHPT has the advantage of bein g able to differentiate this diagnosis from MAH. (C) 2001 Elsevier Science B.V. All rights reserved.