Is the tool easily usable: 
Yes, it relies on simple clinical information

Do the results apply to my patient?
Yes, my patient was typical of a study patient.

Are the results meaningful:
Yes and No.  A 1% risk of ectopic in the low risk group is meaningful. However, the upper confidence limit of 7% is too risky to accept.  Until a larger sample is studied, and the point estimate of ectopic probability for low risk patients is known more precisely, I will not use this decision tool.