From the Guidelines
To rule out rickets, the most appropriate lab tests include serum calcium, phosphorus, alkaline phosphatase, 25-hydroxyvitamin D, and parathyroid hormone (PTH) levels. These tests provide a comprehensive assessment of bone metabolism and vitamin D status, which is crucial in diagnosing rickets. According to the study by 1, calcium and phosphorus levels may be low or normal in rickets, while alkaline phosphatase is typically elevated due to increased osteoblastic activity.
The study by 1 highlights the importance of vitamin D in bone health, and 25-hydroxyvitamin D levels below 20 ng/mL strongly suggest vitamin D deficiency, a common cause of rickets. Elevated PTH indicates secondary hyperparathyroidism, which occurs as the body attempts to maintain calcium homeostasis.
Additional tests may include urinary calcium excretion, renal function tests, and radiographic imaging of wrists and knees to visualize characteristic bone changes. These tests are essential because rickets affects bone mineralization, leading to skeletal deformities and growth impairment. Early detection through appropriate laboratory testing allows for timely intervention with vitamin D and calcium supplementation to prevent permanent skeletal abnormalities.
Some key points to consider when interpreting lab results include:
- Serum calcium and phosphorus levels may be low or normal in rickets
- Alkaline phosphatase is typically elevated in rickets
- 25-hydroxyvitamin D levels below 20 ng/mL suggest vitamin D deficiency
- Elevated PTH indicates secondary hyperparathyroidism
- Urinary calcium excretion and renal function tests can provide additional information on bone health
It is also important to note that vitamin D insufficiency is common in infants and toddlers, but rickets is uncommon, as stated in the study by 1. A systematic clinical, laboratory, and radiologic assessment should exclude the possibility of child abuse in infants with fractures.
Overall, a comprehensive laboratory evaluation, including serum calcium, phosphorus, alkaline phosphatase, 25-hydroxyvitamin D, and PTH levels, is essential in ruling out rickets and guiding appropriate treatment.
From the FDA Drug Label
Ergocalciferol Capsules, USP are indicated for use in the treatment of hypoparathyroidism, refractory rickets, also known as vitamin D resistant rickets, and familial hypophosphatemia. The FDA drug label does not answer the question.
From the Research
Lab Tests to Rule Out Rickets
To diagnose rickets, several lab tests can be used, including:
- Serum calcium levels: to check for calcium deficiency 2, 3, 4, 5, 6
- Serum phosphate levels: to check for phosphate deficiency 2, 3, 4, 5, 6
- Serum alkaline phosphatase levels: to check for bone mineralization defects 2, 3, 4, 5, 6
- Serum 25-hydroxyvitamin D levels: to check for vitamin D deficiency 2, 3, 5, 6
- Parathyroid hormone (PTH) levels: to check for secondary hyperparathyroidism 3, 4
- Urine calcium and phosphate levels: to check for renal tubular defects 3, 4
- Radiographic exams: to check for bone deformities and mineralization defects 2, 3, 4, 6
Interpretation of Lab Results
The interpretation of lab results is crucial in diagnosing rickets. For example:
- Low serum calcium and phosphate levels, along with elevated alkaline phosphatase levels, may indicate rickets 2, 3, 4, 5, 6
- Low serum 25-hydroxyvitamin D levels may indicate vitamin D deficiency 2, 3, 5, 6
- Elevated PTH levels may indicate secondary hyperparathyroidism 3, 4
- Abnormal urine calcium and phosphate levels may indicate renal tubular defects 3, 4
Diagnostic Approaches
The diagnostic approach to rickets may involve:
- Clinical evaluation: to check for signs and symptoms of rickets 2, 3
- Lab tests: to check for calcium, phosphate, and vitamin D deficiencies, as well as bone mineralization defects 2, 3, 4, 5, 6
- Radiographic exams: to check for bone deformities and mineralization defects 2, 3, 4, 6
- Genetic testing: to check for genetic defects that may cause rickets 5