Pharmacovigilance Methods : Passive Surveillance | Pharmacovigilance Notes For BPharm
I. Passive surveillance
• Encompasses all spontaneous AEFI reporting
• from immunization service providers / hospitals / patients
•Up to next levels: state/territory then national (TGA) and then global
a) Spontaneous reports
A spontaneous report is a voluntary communication by healthcare professionals or consumers to a company, regulatory authority or other organization that defines one or
more adverse drug reactions (ADRs) in a patient who was given one or more medicinal products and that does not originate from a study or any structured data collection
scheme. 12 It plays a key role in the identification of safety signals once a medicine is marketed. In various occurrences, spontaneous reports can vigilant a company to rare adverse events that were not noticed in earlier clinical trials or other pre-marketing studies. It can also deliver important information on at-risk groups, risk factors and clinical features of known serious ADRs.
Newly, systematic methods for the recognition of safety signals from spontaneous reports have begun to be used. Several of these methods are static in development and their
utility for identifying safety signals is being assessed. These methods include the calculation of the proportional reporting ratio, as well as the use of Bayesian and other techniques for signal detection.
Data mining techniques have also been used to examine medicine-medicine interactions 20, but these techniques should always be used in conjunction with, and
not in place of, analyses of single case-reports. Data mining techniques facilitate the evaluation of spontaneous reports by using statistical methods to detect potential signals that merit further evaluation. However, this tool does not quantify the magnitude of risk, and caution should be exercised when comparing medicines. Further, when using data mining techniques, consideration should be given to the threshold established for detecting signals, since this will have implications for the sensitivity and specificity of the method (a high threshold is associated with high specificity and low sensitivity).
Confounding factors that influence reporting of spontaneous adverse events are not removed from data mining. The results of data mining should thus be interpreted
with the knowledge of the weaknesses of the spontaneous reporting system and, more specifically, the large differences in the ADR reporting rate for different medicines and the many potential biases inherent in spontaneous reporting. All signals should be evaluated while recognizing the possibility of false-positives. In addition, the absence of a signal does not mean that a problem does not exist.
Advantage & Disadvantage of Passive Surveillance
| Pros | Cons |
| 1.Covers the whole population Includes all medicines | Inherent under-reporting Captures only suspected ADRs |
| 2.Continual monitoring throughout life- cycle of a medicine | Reporting bias-e.g. Seriousness, severity New medicine. Advertising of product, Publicity of specific ADR |
| 3.Detects signals of new, rare or serious ADRs | Difficult to detect |
| 4.Most commonly used method Easiest method to establish Relatively inexpensive | ‒ delayed ADRs & |
| 5.Least labour intensive | ‒ ADRs with high background incidence |
b) Case series
A series of case-reports can deliver signs of an association between a medicine and an adverse event, but they are normally more valuable for producing theories than for
confirming a relationship between medicine exposure and outcome
Notes Compilation
Dr. Vivek Jain