Rachel J M Dennis¹, William M McConnell¹, Paul Glendenning^1,2

¹Biochemistry Department, Clinipath Pathology, 310 Selby St N, Osborne Park, Western Australia, 6017; ²Department of Clinical Biochemistry, PathWest Laboratory Medicine, Royal Perth and Fiona Stanley Hospitals, Perth, WA, Australia

Persistent or severe hypophosphataemia may be under investigated.  We audited the frequency of hypophosphataemia and factors associated with repeat testing, utilising data from the largest private pathology provider in Western Australia. 

Of 61,861 requests for phosphate measurement extracted from Jan-Dec 2023, 179 adult patients with hypophosphatemia (RI <0.7mmol/L) were identified after excluding recent parental iron therapy, Oncology or Haematology care, and results from Fasting Metabolic Bone Studies.  Frequency of repeat testing of phosphate and/or renal phosphate threshold (TmP/GFR) measurement, clinical factors (sex, age), biochemical factors (presence of hyperphosphatasaemia, hyperparathyroidism, abnormal serum calcium, renal impairment, severity of hypophosphataemia), requestor (GP or specialist) and setting (inpatient or outpatient) were examined. 

Most (106 of 179; 59%) had no repeat testing within 6 months.  12 of 73 with repeat testing demonstrated persistent hypophosphataemia; 7 of 12 with persistent hypophosphataemia were GP investigated, 5 specialist managed and 2 of 12 had TmP/GFR measurement. 

Female sex but not age, hyperphosphatasaemia, hyperparathyroidism, abnormal calcium, severity of hypophosphataemia, inpatient/outpatient setting or GP/specialist care, was statistically predictive of repeat testing (p<0.05). 

Hypophosphataemia is under investigated.  Reflex or directive laboratory commenting needs to emphasise the importance of repeat investigation of hypophosphataemia and the utility of TmP/GFR measurement when hypophosphatemia persists. 

Author contribution statement:
We confirm that this work is original. 
 Individual author contributions were as follows: 

- R Dennis: data analysis, drafting abstract   
- W McConnell: data analysis, revision of abstract 
- P Glendenning: supervising author, revision of abstract