84132

Phosphorus; serum

The CPT code 84132 describes the quantitative laboratory analysis of inorganic phosphate levels in a serum blood sample. Phosphorus is a vital mineral that plays a critical role in bone formation, cellular energy production (ATP), and various other metabolic processes. Abnormal serum phosphate levels can indicate underlying disorders related to bone metabolism, kidney function, parathyroid gland activity, or nutritional status. This test measures the concentration of inorganic phosphate in the liquid portion of the blood after it has clotted, providing essential diagnostic information.

Clinical Indications

  • Evaluation of renal dysfunction, including chronic kidney disease, where impaired phosphate excretion can lead to hyperphosphatemia.
  • Diagnosis and monitoring of parathyroid gland disorders, such as hyperparathyroidism (often causing hypophosphatemia) or hypoparathyroidism (often causing hyperphosphatemia).
  • Assessment of bone and mineral metabolism disorders, including osteomalacia, rickets, and unexplained bone pain.
  • Investigation of electrolyte imbalances, particularly in critically ill patients, those receiving total parenteral nutrition (TPN), or individuals with severe malnutrition.
  • Evaluation of vitamin D deficiency or toxicity, as vitamin D plays a crucial role in phosphate absorption and regulation.
  • Monitoring patients on medications that can affect phosphate levels, such as phosphate binders or diuretics.

Procedure Steps

  1. **Patient Preparation**: Typically, no specific fasting is required, but patients may be advised to avoid certain medications or supplements that could interfere with results. Consistent timing relative to food intake may be relevant.
  2. **Sample Collection**: A venous blood sample is drawn from the patient, usually from an arm vein, and collected into a standard venipuncture tube (e.g., serum separator tube or red-top tube).
  3. **Sample Processing**: The collected blood is allowed to clot, then centrifuged to separate the serum from the blood cells.
  4. **Laboratory Analysis**: The serum aliquot is analyzed using automated chemistry analyzers. Common methods involve spectrophotometric assays where inorganic phosphate reacts with a chemical reagent to form a colored complex, the intensity of which is directly proportional to the phosphate concentration.
  5. **Result Reporting**: The measured serum inorganic phosphate concentration is reported, typically in milligrams per deciliter (mg/dL). Results are interpreted in conjunction with the patient's clinical presentation and other relevant laboratory findings (e.g., calcium, parathyroid hormone, creatinine, vitamin D).

Coding Guidelines

  • CPT code 84132 is used for the laboratory analysis of serum phosphorus.
  • This code should be reported once per patient encounter, regardless of the number of aliquots or repeated measurements performed on the same sample during that encounter.
  • Medical necessity must be clearly documented in the patient's medical record, justifying the performance of the test based on clinical indications.
  • While phosphorus may be part of larger comprehensive metabolic panels (e.g., CPT 80053), if ordered as a standalone test or in specific custom panels, 84132 is the appropriate code.
  • Check payer-specific policies for coverage criteria and frequency limitations for serum phosphorus testing.

Associated ICD-10 Codes