ICD-10 Codes for Parathyroid Hormone Testing
The primary ICD-10 codes that support medical necessity for parathyroid hormone (PTH) testing include those related to chronic kidney disease (CKD) stages 3b-5, primary hyperparathyroidism, and disorders of calcium metabolism. 1
Primary Diagnostic Codes That Support PTH Testing
Chronic Kidney Disease-Related Codes
- E83.52 - Hypercalcemia (often used with CKD codes) 1
- N18.3 - Chronic kidney disease, stage 3 (specifically stage 3b with GFR <45 ml/min) 1
- N18.4 - Chronic kidney disease, stage 4 1
- N18.5 - Chronic kidney disease, stage 5 1
- N18.6 - End-stage renal disease 1
Parathyroid Disorder Codes
- E21.0 - Primary hyperparathyroidism 1
- E21.1 - Secondary hyperparathyroidism, not elsewhere classified 1
- E21.2 - Other hyperparathyroidism 1
- E21.3 - Hyperparathyroidism, unspecified 1
- E21.4 - Other specified disorders of parathyroid gland 1
- E21.5 - Disorder of parathyroid gland, unspecified 1
- E20.0 - Idiopathic hypoparathyroidism 2
- E20.8 - Other hypoparathyroidism 2
- E20.9 - Hypoparathyroidism, unspecified 2
Secondary Supporting Diagnostic Codes
Calcium Metabolism Disorders
- E83.50 - Unspecified disorder of calcium metabolism 1
- E83.51 - Hypocalcemia 1
- E83.52 - Hypercalcemia 1
Other Related Conditions
- M83.0-M83.9 - Adult osteomalacia (when related to calcium/phosphate disorders) 1
- M85.80-M85.9 - Other specified disorders of bone density and structure 1
- E55.9 - Vitamin D deficiency, unspecified 1
Clinical Guidelines for PTH Testing
Chronic Kidney Disease
- PTH testing is recommended at least once in adults with GFR <45 ml/min per 1.73 m² (CKD stages 3b-5) 1
- For patients with elevated PTH above the upper normal limit, evaluation should first focus on hyperphosphatemia, hypocalcemia, and vitamin D deficiency 1
Primary Hyperparathyroidism
- PTH testing is indicated for patients with hypercalcemia to distinguish primary hyperparathyroidism from other causes 1
- Normocalcemic primary hyperparathyroidism diagnosis relies on elevated PTH with normal calcium values 1
Important Testing Considerations
Pre-analytical Factors
- PTH is more stable in EDTA plasma than in serum 1
- PTH has a circadian rhythm, which may affect results depending on sampling time 1
- Storage conditions affect stability (PTH is more stable at 4°C than at room temperature) 1
Analytical Factors
- Different assay generations (second vs. third) can yield PTH concentration variations up to 47% 1
- Second-generation assays measure both full-length PTH and fragments (mainly 7-84 PTH) 1
- Third-generation assays measure only full-length PTH 1
Patient-Specific Factors That May Affect Results
- Race (PTH concentration is higher in Black people compared to White people) 1
- Age (PTH increases with increasing age due to declining GFR) 1
- BMI (PTH concentration is higher in obese patients) 1
- Vitamin D status (deficiency increases PTH concentration) 1
Common Pitfalls
- Biotin supplements can interfere with PTH assays, causing either overestimation or underestimation depending on assay design 1
- Lack of standardization between different PTH assays can lead to significant differences in results between laboratories 1
- Reference values vary based on vitamin D status, BMI, race, age, and the specific assay used 1