TABLE 4.

Analysis of false negatives

Number	Search strategies (n = 139)		n	%
	Missing conjugations of	Drug‐induced	3	2.2
		Allergy	0	0.0
		Side effect	3	2.2
		Intolerance	0	0.0
		Reaction	0	0.0
		Toxicity	0	0.0
S1	Potential improvement: Using keywords implying ADRs		6	4.4
	>16 characters between the preposition and drug name		2	1.4
	Missing synonyms for drug names		44	31.7
	Missing abbreviations		6	4.3
	Missing prepositions		2	1.4
	DD		3	2.2
S2	Potential improvement: Using prepositions followed closely a by a drug group b , d , a generic drug name, a drug brand, trade name or abbreviation a drug, or drug therapy c , d		57	41.0
S3	Potential improvement: In ADRs found in labelled allergy and anaphylaxis forms		0	0.0
	Specific missing complication fields		3	2.2
S4	Potential improvement: Content of complication registration containing key field drug‐induced		3	2.2
S5	Potential improvement: Found in ADR module		0	0.0
	MedDRA + drug name		3	2.2
	Drug name + MedDRA		24	17.3
	Missing synonym of MedDRA term		2	1.4
aS6	Opportunity for additional strategy: MedDRA term mentioned in text combined with drug name d		29	20.9
	Cannot tolerate		2	1.6
aS7	Opportunity for additional strategy: Abbreviations of cannot tolerate		2	1.6
	No obvious additional strategy e		42	30.2

Abbreviations: ADR, adverse drug reactions; DD, differential diagnosis.

^a The maximum number of characters between the preposition and drug was 16.

^b Drug group names used were based on the ATC therapeutic subgroup, pharmacological subgroup, chemical subgroup or chemical substance (ie, second to fifth levels of ATC main groups classified by WHO).

^c Examples being PPI (proton‐pump inhibitor), HCTZ (hydrochlorothiazide), FOLFOX (combination therapy of fluorouracil and oxaliplatin). A full list of abbreviations is provided in Table S2.

^d MedDRA term and drug name are mentioned within 16 characters of each other.

^e No simple rule‐based strategy was thought of to identify these ADRs.