Patient-initiated postmarketing surveillance: a validation study

Age Effects on Patient Drug Attribution Judgments

Data were obtained on patients' attribution of symptoms using two different post-marketing surveillance methods. In the patient-initiated method, outpatients were randomly assigned to have a printed notice conspicuously attached to the outside of their medication bags; the "outsert" requested the patients to monitor themselves during the next 2 weeks and to report via a toll-free telephone number any new or unusual symptoms. In the staff-initiated method, other patients filling the same target drug prescriptions did not receive any outsert but were identified at the pharmacy for a telephone interview 10 to 14 days later. The target drugs were chosen from two classes for which the major adverse drug reactions (ADRs) are well identified: oral antibiotics and tricyclic antidepressants. During the interview, for each reported symptom the patient was asked whether it might have been caused by the target drug. Results indicated that older patients, irrespective of the surveillance method or the drug class, appear to be capable of discriminating probable ADRs at least as well as or possibly better than younger patients.

Initial development and testing of an instrument for patient self-assessment of adverse drug reactions

PURPOSE

To develop and conduct preliminary testing of a causality assessment tool for patients, for potential use in encouraging both discussions with clinicians about suspected adverse drug reactions (ADRs) and reporting to authorities.

METHODS

Ten causality statements, developed from qualitative studies involving patients, with a scoring system allowing categorization, were embedded in a questionnaire which also included a symptom checklist and additional details about one suspected ADR and medicine, selected for causality assessment. Patients with experiences of suspected ADRs were involved in cognitive interviews (15), piloting (20) and psychometric testing (120). Test-retest reliability, construct validity and criterion-related validity were evaluated, through repeated causality assessment, comparison with a visual analogue scale assessing certainty of causality and comparison with causality assessment using World Health Organization-Uppsala Monitoring Centre (WHO-UMC) criteria, respectively. The study involved outpatients at a university hospital in northeast Thailand.

RESULTS

Ninety-eight patients completed causality assessment twice: both causality scores (Spearman rs  = 0.715; p < 0.001) and causality classification [percentage of positive agreement (PPA) = 68.4; κ = 0.419; p < 0.001] showed satisfactory reliability. Causality scores were positively correlated with certainty of causality (Spearman rs  = 0.556; p < 0.01). There was moderate agreement against WHO-UMC criteria [PPA = 70.4; κ = 0.440; p < 0.001]. Of the 91 completing an evaluation, 88% agreed that the tool should be used routinely, 78% agreed that it gave them useful results and 80% agreed that it was easy to use.

CONCLUSIONS

This novel instrument has satisfactory psychometric properties and was acceptable to Thai patients, but it requires further testing. It has potential for use in supporting patients with suspected ADRs to discuss these with health professionals, and perhaps to report directly.

Patient reporting of suspected adverse drug reactions to antiepileptic drugs: factors affecting attribution accuracy

This study was aimed to assess the frequency and number of suspected ADRs reported by patients taking antiepileptic drugs (AEDs) and to explore the factors that may affect patients' symptom attribution accuracy. A validated questionnaire containing an extensively checklist of symptoms was distributed to outpatients prescribed one or more AEDs. Data on concomitant drugs and diseases were obtained from outpatient records. All symptoms identified were assessed for causality. Of 1388 questionnaires distributed to 1214 patients, 830 completed questionnaires were returned (59.8%) from 727 patients. In total, 7815 symptoms were identified on 757 questionnaires (91.2%). Symptom severity ratings were positively related to the number of symptoms reported (p=0.003). Causality assessment found that 71.9% of the symptoms were 'true' ADRs and 28.1% were 'false' ADRs. Attribution accuracy was primarily influenced by the number of symptoms identified and indication for AED therapy, fewer symptoms and use for non-epilepsy indications being associated with greater attribution accuracy.

Patient reporting of potential adverse drug reactions: a methodological study

AIMS

To develop a systematic generic method of enabling patients to report symptoms which they believe to be due to a particular prescribed drug.

METHODS

A piloted body system-based questionnaire was distributed to patients registered with 79 medical practices in Grampian prescribed one of nine recently marketed 'black triangle' drugs. These comprised four antidepressants, three antiepileptics and two analgesics. This requested respondents to identify any symptoms experienced over the previous year which they thought could be due to the 'black triangle' drug they had used. A sample of medical records was examined to compare symptoms recorded with those reported by patients. A classification system was developed for the study to enable the assessment of symptoms reported for their potential relationship to patients' drug therapy. All symptoms reported were classified, taking into account information provided by patients on their concomitant drugs and diseases. A specialist pharmacist independently re-classified a sample of the symptoms to validate the process.

RESULTS

A 36.3% response rate was obtained (837/2307) with 742 respondents (88.6%) reporting at least one symptom. The median per patient was 6.0 (range 0--71), with almost half (406, 48.5%) reporting fewer than five symptoms. Most symptoms (71.0%) were classified as being probably or possibly related to the drugs studied. Agreement between researcher and specialist on the classification of 75.3% of 716 symptoms was obtained (Kappa=0.563). Responses from patients prescribed antidepressant drugs were more likely to include symptoms potentially caused by these drugs (74.5% of all symptoms reported) than those from patients prescribed analgesics (67.4%) or antiepileptics (65.1%, chi2 = 23.858, d.f. = 2, P < 0.001). Patients reporting large numbers of symptoms were more likely to report some which were classed as unlikely to be an ADR or unattributable (chi2 = 80.587, d.f. = 3, P < 0.001). Of the 742 reporting symptoms in questionnaires, 402 (54.2%) claimed to have reported some or all of these to their doctor. Only 162 (22.6%) of 716 patient-reported symptoms were documented in the primary care medical records of 103 patients prescribed tramadol or venlafaxine.

CONCLUSIONS

Respondents were clearly willing to report symptoms, the majority of which were classed as possibly/probably related to the drugs studied. The results suggest that patients do not report all symptoms they suspect to be ADRs to their GP and that GPs do not record all symptoms which may be reported to them. The method could help to identify problems which patients perceive as being related to their drug therapy and contribute to increased ADR reporting.

Drug use in non-hospitalized children

The knowledge of the characteristics of the use of drugs in non-hospitalized children is of paramount importance since clinical trials are seldom (and sometimes should not be) performed in such patients. The source of drug prescriptions varies a lot: 'self-administration' through parents accounts for as much as formal physician's orders or pharmacist's counselling. Data can be collected through the whole drug chain: drug prescription--drug dispensing--drug attainment--drug consumption. Both qualitative and quantitative data are to be collected in order to draw a complete picture of drug use in non-hospitalized children. Longitudinal collection methods, as well as time-point or cross-sectional studies can be carried out. The particular role of each of these methods of performing a drug utilization study in children are analysed and discussed.

Patients as a direct source of information on adverse drug reactions

To determine whether patients should participate directly in detecting adverse reactions to drugs their ability to provide written reports of symptoms experienced during treatment with amoxycillin or trimethoprim-sulphamethoxazole was investigated. When compared with telephone interviews forms on which patients reported events were reliable (the observed agreement with the same statements posed during telephone calls was 85%, kappa = 0.56) and valid (sensitivity = 54%, specificity = 94%). Patients were also supplied with forms that invited them to report adverse reactions, and their perceptions were compared with those of a panel of experts, who were informed of all clinical events that had been reported during the detailed telephone interviews. Patients were more conservative than the experts in attributing clinical events to drug treatment. The extent of agreement varied and was notably poor for skin and bowel complaints (kappa = 0.13 in each case). The performance of event report forms and reaction report forms as instruments of detection was compared in a hypothetical situation in which the experts' views represented the "truth" about adverse reactions to a new drug. Event reporting had a higher sensitivity than reaction reporting (42% v 24%) but a lower specificity (58% v 98%). National centres monitoring adverse drug reactions should probably resist pressure to accept reports of reactions directly from the public, but a system based on large scale reporting of events might be valuable in aiding the early detection of symptomatic reactions to new drugs.