ABSTRACT
Alkaline phosphatase (AP) has several isoforms including bone alkaline phosphatase (BAP). We evaluated BAP and AP for screening for bone metastasis (BM) in patients with solid tumours. This is a prospective non-blinded study conducted at ABC Foundation School of Medicine Oncology clinics. A total of 40 subjects without a history of cancer and 62 patients with various solid tumours referred for a bone scan had serum drawn for BAP and AP determination. Bone alkaline phosphatase and AP levels in patients with cancer and BM, without BM and with no cancer, were 70.32 +/- 3.65 and 310.21 +/- 16.87 U/L; 41.40 +/- 2.80 and 113.23 +/- 12.95 U/L; 21.19 +/- 2.76 and 148.05 +/- 12.79 U/L respectively (P < 0.0001 for both AP and BAP). For BAP and AP sensitivity, specificity, positive and negative predictive values were 0.86 and 0.52; 0.69 and 1; 0.45 and 1; 0.94 and 0.87 respectively. ROC AUC value for BAP was 0.89 and for AP was 0.93. We conclude that BAP is more sensitive than AP, whereas AP had a remarkable specificity of 100%. In screening for BM in patients with solid tumours, obtaining initially BAP and then selecting for further investigation only patients with an abnormal AP may be a cost and resource saving strategy.
