Patient literature usefulness index
| Variable | Variable name | Weighting | Variable description |
| A | Guideline content percentage compliance (eg, SIGN) | 45 | Straight compliance percentage |
| B | Readability score (%) | 25 | Average score based on two or more readability tests |
| C | RNIB compliance (%) | 20 | Percentage compliance |
| D | Standard information compliance (%) | 10 | Straight compliance percentage |
Patient literature usefulness index=0.45A+0.25B+0.2C+0.1D.
A, every pointer in a given SIGN guideline leaflet is assigned 1 point, and the score is calculated by the overall percentage compliance on all points as per SIGN 46 in this example; B, readability tests score-scaled 1–100 and averaged; C, all 17 points in RNIB-CPG are assigned 1 point, and the score is calculated as a percentage; D, contact information for healthcare service, patient signoff, document name, publication date/version number, date seen. Overall, score as a percentage based on a count of all the items recommended for inclusion.