Phimphilai et al reported a score for predicting hypocalcemia after parathyroidectomy for secondary hyperparathyroidism. This can help to identify a patient whose serum calcium should be monitored more closely. The authors are from Chiang Mai University in Thailand.
Patient selection: parathyroidectomy in secondary hyperparathyroidism
Parameters:
(1) duration of renal replacement therapy (RRT) in years
(2) preoperative serum phosphate in mg/dL
(3) preoperative serum alkaline phosphatase in U/L
(4) means difference of serum parathyroid hormone in percent (based on pre and post operative serum PTH concentration), with PTH reported in pg/mL
The derivation of the mean difference is not given but presumably is:
means difference =
= ((pre-PTH) - (post-PTH)) / (pre-PTH) * 100%
|
Parameter
|
Finding
|
Points
|
|
duration of RRT
|
<= 5 years
|
0
|
|
|
> 5 years
|
1
|
|
serum phosphate
|
< 5 mg/dL
|
0
|
|
|
>= 5 mg/dL
|
1
|
|
serum alkaline phosphatase
|
< 387 U/L
|
0
|
|
|
>= 387 U/L
|
1
|
|
means difference
|
< 97%
|
0
|
|
|
>= 97%
|
1
|
where:
• The cut-off for means difference in PTH is suspicious. In Table 1 the data suggests that 90% or 92% might be more appropriate. To get a 97% difference requires values unlike those shown in Table 1.
total score =
= SUM(points for all of the parameters)
Interpretation:
• minimum score: 0
• maximum score: 4
• A score >= 2 is high risk for hypocalcemia.
Performance
• The area under the ROC curve is 0.76.
