Phosphate

Keywords: PO4, PHOS

Specimen:

5 mL blood in lithium heparin or plain tube.

Rapid separation is essential.

A fasting specimen should be collected if hypophosphataemia is suspected to be due to post-prandial depression of phosphate.

Method:

Spectrophotometry.

Reference Interval:

See Table 6.

Application:

Assessment of patients with renal failure, metabolic bone disease, hyper- and hypo-parathyroidism.

Interpretation:

Increased phosphate levels are found in response to low parathyroid hormone levels (eg, Hypoparathyroidism, Hypercalcaemia due to malignancy and other non-parathyroid causes) and in renal failure.

Decreased levels of phosphate are usually found in patients with primary Hyperparathyroidism, in some cases of Hypercalcaemia associated with malignancy, in renal tubular disorders and in patients using magnesium and aluminium containing antacids.

Levels may be decreased during prolonged intravenous therapy if phosphate supplementation is inadequate. Phosphate levels may also be decreased following a carbohydrate-rich meal, due to cellular uptake of phosphate.

Numerous other conditions can affect serum phosphate levels.

Reference:

Yu G.C. et al. West J Med. 1987; 147: 569-576.