Spurious Hyperphosphatemia in Patients on Hemodialysis With Catheters

Routine phosphate results from patient 1 during 12 months. To convert plasma phosphate in mg/dL to mmol/L, divide by 0.3229.

Phosphate levels in blood from a healthy volunteer measured in a 4.5-mL blood volume. Baseline plus the result after the addition of 35, 70, and 105 μL of alteplase show a linear increase in phosphate concentrations. To convert phosphate in mg/dL to mmol/L, divide by 0.3229.

Whiskers plot of phosphate levels from patient 2 during 1 year on days that alteplase had been instilled into the catheter and on days without alteplase. The mean and range of the values are higher on days after alteplase compared with draws on days without alteplase. The single outlying value of 11.8 mg/dL (closed square) was obtained after the patient skipped 2 consecutive hemodialysis sessions during vacation. To convert phosphate in mg/dL to mmol/L, divide by 0.3229.