Table 1_Laboratory-based case finding using phosphate and alkaline phosphatase to identify genetic and nutritional rickets in children.xlsx

Hypophosphatemia was observed in 2,281 phosphorus measurements (9.98%), and elevated alkaline phosphatase in 3,301 measurements (14.3%). Fifty-five laboratory tests (0.31%) from 37 patients simultaneously met the criteria for hypophosphatemia (<−2 SD) and elevated alkaline phosphatase (>+2 SD); 56.8% were male, with a mean age of 6.5 ± 6.0 years. Following clinical review, 15 patients (40.5%) were classified as having a bone mineral metabolism disorder, including 10 with osteopenia of prematurity, three with nutritional rickets, one with a pathogenic variant in PHEX, and one with osteoporosis in the context of ReNU syndrome; 10 patients (27.0%) were classified in the acute/critical illness group and 12 (32.4%) in the other category.

Radiographs were available in 30 patients, with findings consistent with rickets in three (10%). One previously unrecognized case of mild nutritional rickets was identified.</p>Conclusions<p>Laboratory-based case finding using phosphorus and alkaline phosphatase may help identify pediatric bone metabolism disorders, including forms of rickets. Combined hypophosphatemia and elevated alkaline phosphatase may be useful for guiding etiological investigation.

This approach may complement clinical evaluation and facilitate earlier diagnosis. Early identification is clinically relevant because treatments can modify disease course and reduce long-term complications in children with confirmed forms of rickets, when appropriate.</p>