Each report identified during the review was considered and
evaluated for causality according to the WHO causality standard
approach (WHO, 2004). The assessment was based on: (1) the
association in time between administration of the PFS and the
adverse event; (2) the outcome of de-challenge and re-challenge
(when present); (3) known pharmacology; (4) medical or
pharmacological plausibility (the sequence of symptoms, signs,
laboratory tests, pathological findings and knowledge of mechanisms);
(5) likelihood of other causes or their exclusion; (6) testing
for adulterants or contaminants that could be the source of adverse
events; (7) inappropriate use (WHO, 2004).