Table 1

Clinical assumptions in decision model

AssumptionLikely effect on estimated outcomesGeneralisability
No change in the clinical quality of care at health facility level (ie, ANC visit quality) due to the community-level quality intervention.Would be more likely to improve.
Conservative assumption; underestimates benefit.
Largely reflected in real-life field observations that no improvement happened without additional inputs at facility level.
Patients adhere to treatment as prescribed.If adherence is poor, some outcomes will be worse in both arms (possibility 1), so no effect.
If adherence is higher in the intervention arm, then our assumption would mean we are underestimating the benefits (possibility 2).
A patient’s relationship with community health worker may impact adherence.
In real life:
Syphilis treatment stock-outs frequent.
HIV treatment well taken.
Iron not taken well—people stop this.
TPHA assumed perfect sensitivity/specificity.Some people with previously treated syphilis will still have positive TPHA on a rapid test, resulting in (low) overestimate of prevalence, therefore slightly overestimating benefit.Some people who do not have active syphilis may get unnecessary treatment.
No confirmed HIV diagnosis (single test only).A few people with a first positive result will have a false positive (<4/1000). Overestimate of prevalence may result in slight overestimate of benefit.Unlikely to influence results or generalisability to other contexts.
No interactions between diseases/comorbidities.Likelihood of infection with each disease was treated as independent variable. This overestimates the number who benefits from intervention but underestimates the size of the benefit because of increased severity.Treatment selection may vary by comorbidity (we have used data on the first-line treatment rates for uncomplicated single infections).
Prematurity overlaps with low birth weight.Gestational age is difficult to measure.In the model we have not considered gestational age as an outcome given this is violation of independence. Association of prematurity with different diseases considered in the model is less clear, but we recognise this as an important infant outcome that also influences mortality.