Rather than excluding high risk groups, we present stratified risk estimates for high risk conditions associated with frequent stimulant use.
A sensitivity analysis excluding high risk for bias studies produced a slightly increased prevalence of 19.5% (95% CI 2.3-36.8).
We conducted a sensitivity analysis to exclude high risk studies in order to provide less biased estimates.
When we excluded "high risk" cases (regardless of survival) from the entire IMA dataset, the perinatal mortality rate, at 4.8/1000, is comparable with the national rate.
However, the perioperative risk with carotid endarterectomy is mainly defined by clinical risk factors that are usually available at first encounter with patients and may have served to exclude high risk patients from inclusion in a study.
Reasons given for the goal of delivery within 24 h of ripening (excluding high risk pregnancies) are usually cited as maternal preference [ 20] and the cost of hospitalization (which would self evidently not be relevant in outpatient management).
Fourthly, there were few data on children with comorbidities, with only a single trial of children with asthma: trials excluded "high risk" children such as those who are immunosuppressed or with chronic cardiac or respiratory problems.
When interpreting the results, the selection of the study population has to be kept in mind: risk-pregnancies due to maternal disease and multiple gestations have been excluded from the analysis so that we do not know if there is any association of the amount of folate intake from diet or supplements with spontaneous PTD in the excluded high risk pregnancies.
Thirteen studies (19%) limited inclusion of patients to lower risk patients (category A) by including only patients with less severe diabetes [ 20, 26, 27, 31- 33] or patients on monotherapy [ 19, 24, 27, 33- 36], or OAD-naïve patients [ 27, 35] or by excluding high risk patients who failed previous therapy [ 37] or with multiple comorbidity [ 20, 38, 39].
For both unadjusted and adjusted data, stratified meta-analyses by study-level characteristics identified studies with prospective follow-up or those conducted at multi-center or ICU as less heterogeneous (Additional file 2: Table S2-S3); howexcludingluding high risk of bias studies did not change the overall estimate or measures of consistency (I 2 ).
The school based study population excludes high-risk adolescents or adolescents with severe symptoms not attending school.
