The assessment of adverse reaction case reports needs combined expertise in clinical medicine, pharmacology and toxicology, and epidemiology. This expertise can be developed by training the centre’s staff and by the use of specialised consultants. In the assessment of case reports the following elements can be recognised:

1. Quality of documentation (e.g. completeness and integrity of data, quality of diagnosis, follow-up). The basic elements of a case report are listed in § 4.1.

2. Coding. Drug names should be registered in a systematic way, for example by using the WHO Drug Dictionary (which is based on the INN nomenclature and the ATC classification). For the coding of the adverse events the WHO Adverse Reaction Terminology (WHOART), or another internationally recognised terminology (e.g. MedDRA) should be used.

3. Relevance with regard to the detection of new reactions, drug regulation, or scientific or educational value. The following questions especially may be asked:

• New drug? Products on the market less than five years are usually considered new drugs

• Unknown reaction? (i.e. not included in the approved Summary of Product Characteristics or ‘unlabelled’). Also important is whether the reaction is described in the literature, e.g. national drug formulary, Martindale, Meyler’s Side Effects of Drugs. (Ask the Uppsala Monitoring Centre for books and other information sources)

• Serious reaction? (See Glossary).

4. Identification of duplicate reports. Certain characteristics of a case (sex, age or date of birth, dates of drug exposure, etc.) may be used to identify duplicate reporting.

5. Causality assessment or imputation. With few exceptions, case reports describe suspected adverse drug reactions. Various approaches have been developed for the structured determination of the likelihood of a causal relationship between drug exposure and adverse events, for example by the WHO Drug Monitoring Programme (see Glossary), the European Commission, and the French national pharmacovigilance programme. These systems are largely based on four considerations:

• the association in time (or place) between drug administration and event

• pharmacology (including current knowledge of nature and frequency of adverse reactions)

• medical or pharmacological plausibility (signs and symptoms, laboratory tests, pathological findings, mechanism)

• likelihood or exclusion of other causes.

The WHO causality categories have the advantages of being internationally agreed and easy to use. Definitions for selected adverse reactions have been worked out and reached by international agreement. For some of these reactions special causality algorithms have also been developed (Bénichou, 1994).