SUN-LB73 Is It Possible to Optimize Resources in Bone-Alkaline Phosphatase Medical Request?

INTRODUCTION: Bone metabolism assessment includes total alkaline phosphatase (ALP) and more specifically the bone-alkaline phosphatase (BAP) as markers of bone formation. Its measurement is important for diagnosis and in bone pathology treatment following-up. In our setting, a ten-fold price for BAP has raised the necesity to review in how many cases its request has been justified. AIM: Establish through an appropiate statistical analysis, cut-off values of ALP that could guarantee to perform BAP measurements. Its analysis would allow us to make a demand adequacy. MATERIALS AND METHODS: A retrospective study was carried out on laboratory analysis orders of 405 adult women. We separate them into the following groups: (G1): 48 premenopausal womens (pre) and 357 post menopausal women (pos): (G2)133 <60 years-old, (G3)135: 60-69 years-old and (G4)89: >70 years-old. All patients had measurements of both analytes; ALP (colorimetric method, Roche Cobas, Reference value (RefV)=40-130 UI/L) and BAP (QLIA, Liaison Diasorin, RefV pre=3-19 ug/mL, pos=6-26 ug/mL). Statistic analysis: ROC-Plot to define cut-off value (we define as true positive BAP values over RefV). Kruskal Wallis, Dunn test to compare all the groups. RESULTS: (median and range): ALP(UI/L) G1: 81(38-265) G2: 88(47-211)*, G3: 85(39-213) y G4: 80(40-138) (*p<0.05 G2vsG4). BAP (ug/L) G1: 13.6(5.1-106), G2: 14.3(3.5-61.5)*, G3: 13.9(2.9-52.5) and G4: 11.6(2.0-29.6), (*p<0.05 G2vsG4). We observe that 73% of G1, 93.5% of G2, 92.6% of G3, 97.7% of G4 has showed normal values. The ROC plot analysis showed the best cut-off for ALP in G1=87 (S=92%,Sp=85%,AUC=0.955). If, using this cut off we had processed 18 BAP which 6 patients would have been normal (33.4%). In G2=127 (S=100%, Sp=97.6%, AUC=0.996) using this cut off we had processed 13 BAP, which 4 patients would have been normal (30.8%). Meanwhile in G3=102(S=100%, Sp=85.6%, AUC=0.97) we had processed 30 BAP and G4=120 (S=100%, Sp=96.5%, AUC=0.966) we had processed only 6 BAP. CONCLUSIONS: Application of the calculated cut-off allowed us to investigate 97% of the pathological BAPs. The measurement of ALP first, would guarantee to process only 17% of the requested BAPs. This suggestion would result in a significant saving of our resources, maintaining the quality of care. It is necessary to apply cut-off according to age to justify the BAP assesment. Physicians must define the appropriate exceptions.