Sir,

We note with interest the paper by Jones et al regarding the role of General Practitioners with specialist interests (GPwSI) in reducing the high false-positive rate of referrals for glaucoma.1 They maintain that the reduced false-positive rate in their study translates into improved efficiency. However, efficiency is characterised by maximum effectiveness with minimum waste of resources. Measurement of efficiency would also require demonstration of a reduced false-negative rate. It would be of interest to know how many of the patients discharged by the GPwSI would also have been discharged by the glaucoma specialist.