Appendix 1: Levels of evidence used by CHS consensus group to rate studies on hypertensive disorders in pregnancy relating to diagnosis and prognosis and to grade recommendations*
Levels of evidence for rating studies of diagnosis
I.	(a) Independent interpretation of test procedure (without knowledge of result of diagnostic standard) (b) Independent interpretation of diagnostic standard (without knowledge of result of test procedure) (c) Selection of patients or subjects who are suspected but not known to have the disorder of interest (d) Reproducible description of both the test and the diagnostic standard (e) At least 50 patients with and 50 without the disorder
II.	Meets 4 of the criteria in I
III.	Meets 3 of the criteria in I
IV.	Meets 2 of the criteria in I
V.	Meets 1 of the criteria in I
VI.	Meets none of the criteria in I
Levels of evidence for rating studies of prognosis
I.	(a) Inception cohort (b) Reproducible inclusion and exclusion criteria (c) Follow-up of at least 80% of subjects (d) Statistical adjustment for extraneous prognostic factors (confounders) (e) Reproducible descriptions of outcome measures
II.	Inception cohort but meets only 3 of the other criteria in I
III.	Inception cohort but meets only 2 of the other criteria in I
IV.	Inception cohort but meets only 1 of the other criteria in I
V.	Inception cohort but meets none of the other criteria in I
VI.	Meets none of the criteria in I
Grading system for recommendations
A.	The recommendation is based on 1 or more studies at level I
B.	The best evidence available was at level II
C.	The best evidence available was at level III
D.	The best evidence available was lower than level III and included expert opinion
*Taken from Carruthers et al,18 with permission.

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