In this lecture I discuss Methods of Causality assessment. Various basis of casualty determination. As well as grading of casualty of ADR.
MCQ on Causality Assessment also discuss.
The causality assessment for adverse drug reactions
(ADRs) is challenging, and none of the diferent method
available for assessing the causality of ADR is accepted
as the gold standard.
• The causality assessment of adverse drug reactions by
updated Logistic method and Naranjo algorithm are less
prone to subjective variations compared to the World
Health Organization-Uppsala Monitoring Center (WHOUMC) system.
• Though WHO-UMC causality assessment method is
easy, other objective methods like Narango algoritm and
updated logistic method should be used in combination
with WHO-UMC method to reduce the subjective variability.
Causality assessment remains a valuable approach in
pharmacovigilance to detect a causal link between an
adverse event and a drug treatment. Various types of
tools or assessment methods are available to assess the
causal relationship between a drug and an adverse event
which are broadly based on three main approaches namely
expert judgement or global introspection, algorithm-based
approaches, and probabilistic or Bayesian approaches
Causality assessment methods like Swedish method, World
Health Organization-Uppsala Monitoring Centre (WHOUMC) system are based on expert judgement. Naranjo,
Karch and Lasagna, French, Kramer, Begaud, Jone, Maria
and Victorino, RousselUclaf causality assessment method
(RUCAM) are algorithm based causality assessment methods. Australian, Bayesian Adverse Reactions Diagnostic
Instrument (BARDI), MacBARDI and the recently developed updated Logistic method are based on probabilistic or
Bayesian approach. Though various methods are used
for causality assessment of adverse drug reactions (ADRs),
none of the methods is accepted as the best for analyzing the
causality and each method has its own advantages and limitations. WHO-UMC method is used as practice tool for
reporting of individual adverse event reports by the national
centers participating under International Drug Monitoring
Program. Likewise, Naranjo algorithm, which was initially developed for adverse event monitoring in clinical trial,
is also used by healthcare professional for assessing adverse
events. The pharmaceuticeutical industries use these methods for initial case processing but the fnal reports are given
to the regulatory authorities in binary terms like ‘related’ or
‘not related’.
The WHO-UMC system is a universally accepted method
for causality assessment. Although it is comparatively easy
for analysis and less time consuming, at the same time
several disadvantages have been described, such as high
dependency on individual expertise and judgement for
assessment, weak and poor reproducibility in the WHOUMC system, and moreover individual categories are not
sharply delineated. Naranjo algorithm is rather
simple and brief. It is the most extensively used method
discerning scores for each point which reduce intra and
inter-observer variation and had good reproducibility. But
the disadvantages of this method are lack of sensitivity for
the ‘uncertain’ category resulting in low score for certain
type of ADRs, not valid in children, not appropriate to use
in critically ill patients, organ toxicities, drug overdose, and
drug-drug interactions . The probabilistic approach,
based on Bayesian theorem provides results in the form of
probability of causation of an adverse event. Although
regarded as the most reliable approach, the methods used
based on this approach are not suitable for routine practice
because these are complex and time-consuming .
In 2006 Researchers reported a new method of
causality assessment known as the Logistic method based
on the probabilistic approach which was again updated
in 2012. Although comparisons among various methods are mentioned in many articles, the comparison among Logistic methods and other methods are mentioned in very few articles. WHOUMC causality assessment system takes into account the
clinical-pharmacological aspect , whereas the Naranjo
algorithm assigns scores to these aspects, such as temporality and alternative explanations, as well as to the responses
to additional questions. Though there are some published articles comparing WHO-UMC system and Naranjo
algorithm , comparison among WHO-UMC
system, Naranjoalgorithm and updated Logistic method are
lacking.
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