Bu Deloitte yn cydweithio â'r Bwrdd Iechyd a swyddogion Llywodraeth Cymru drwy gydol yr adolygiad, ac roedd yn canolbwyntio ar bedwar ffactor cyffredinol sy’n effeithio ar gostau  iechyd (demograffeg, pellter, graddfa ac effeithlonrwydd). Ar gyfer pob un o'r ffactorau hynny, datblygwyd amcangyfrifon o gostau ychwanegol Hywel Dda drwy gymharu costau'r Bwrdd Iechyd â chyfartaledd Cymru.
Deloitte’s worked collaboratively with both Health Board and Welsh Government officials throughout the review, and their approach to the review focused on four broad drivers of health costs (demographics, remoteness, scale, and efficiency). For each of the 4 drivers, estimates of excess costs experienced by Hywel Dda were developed by comparing the Health Board’s costs to the Welsh average.