**3.6 Serum phosphate of subjects**

The mean serum phosphate in the CRF group was 6.1 + 2.0mg/dl, and this was significantly higher than the mean serum phosphate of 3.2 + 0.6mg/dl in the control group (p<0.05). Table 7 shows the pattern of serum phosphate in both the CRF and control groups. In the CRF group, 41 (79%) patients had hyperphosphataemia, while 11 (21%) had normal serum phosphate levels. No patient had hypophosphataemia. In the control group, all the 40 (100%) patients had normal serum phosphate levels. There was insignificant but positive correlation between serum phosphate and creatinine clearance (r = 0.1) and bone pain (r = 0.4). (See Table 7)


Table 7. Pattern of serum phosphate in subjects.

Amongst the CRF patients with serum alkaline phosphatase of <25iu/l, the mean serum phosphate was 5.1 + 0.9mg/dl, while in the group with serum alkaline phosphatase of 25 – 95iu/l, serum phosphate was 6.5 + 1.2mg/dl, and in the group with serum alkaline phosphatase of >95iu/l the mean serum phosphate was 6.2 + 1.4mg/dl. Thus, there was a weak but negative correlation between serum phosphate and total serum alkaline phosphatase (r – 0.15), such that when total serum alkaline phosphatase was increasing, the serum phosphate also increased.

Amongst the CRF patients with creatinine clearance of >30mls/min, the mean serum phosphate was 4.4 + 1.2mg/dl, while in the groups with creatinine clearance of 15 – 29mls/min and <15mls/min (ESRD), the mean serum phosphate was 6.6 + 1.1mg/dl and 6.2 + 1.3mg/dl respectively. As the creatinine clearance tended towards ESRD, the serum phosphate rises. There was a positive correlation between serum phosphate and creatinine clearance (r = 0.10).
