When should I consider referring a patient with phosphate disorders to secondary care for further evaluation?

Consider referring a patient with phosphate disorders to secondary care for further evaluation if:

• They have chronic kidney disease (CKD) with a glomerular filtration rate (GFR) less than 30 ml/min/1.73 m² (CKD stage 4 or 5), especially if serum phosphate, calcium, or parathyroid hormone (PTH) levels are abnormal or difficult to control. Specialist advice is recommended when there is uncertainty about management or monitoring frequency in this group.
• They remain hyperphosphataemic despite maximal tolerated doses of phosphate binders, or if they require complex combinations of phosphate binders to control serum phosphate.
• There are complications related to phosphate disorders such as persistent symptoms of CKD-mineral and bone disorder despite correction of vitamin D deficiency and initial treatments.
• There is suspicion of primary hyperparathyroidism or other causes of phosphate imbalance, especially if serum calcium is elevated (albumin-adjusted serum calcium ≥2.6 mmol/l) or PTH levels are abnormal, warranting specialist assessment.
• There are difficulties in managing phosphate binders due to intolerance, side effects, or off-label use considerations requiring specialist input.

Referral to renal or endocrine specialists is appropriate for detailed assessment, management of mineral and bone disorders, and consideration of advanced therapies or investigations beyond primary care scope ¹,².