Adverse Drug Reaction Probability Scale (Naranjo)
What is Naranjo - ADR Probability scale
The
Naranjo Algorithm, or Adverse Drug Reaction Probability Scale, is a method by which to assess whether there is
a causal relationship between an identified untoward clinical event and a drug using a
simple questionnaire to assign probability scores.
Adverse Drug
Reaction Probability Scale (Naranjo) in Drug Induced Liver Injury
This
scale was developed to help standardize assessment of causality for all
adverse drug reactions and was not designed specifically for drug induced liver injury. The scale was also
designed for use in controlled trials
and registration studies of new medications, rather than in routine clinical practice. Nevertheless,
it is simple to apply and widely used.
Many publications on drug induced liver injury mention results of applying
the ADR Probability Scale.
The ADR Probability Scale consists of 10 questions that are answered
as either Yes, No, or “Do not
know”. Different point values (-1, 0, +1 or +2) are assigned to each answer. A simplified version of the 10
questions is provided below:
1.
Are there
previous conclusive reports
of this reaction?
2.
Did the adverse
event appear after the drug was given?
3. Did the adverse reaction improve when the drug was discontinued or a specific antagonist was given?
4.
Did the adverse reaction
reappear upon read ministering the drug?
5.
Were there
other possible causes for the reaction?
6.
Did the adverse
reaction reappear upon administration of placebo?
7. Was the drug detected in the blood or other fluids in toxic concentrations?
8. Was the reaction worsened upon increasing the dose? Or, was the reaction lessened upon decreasing the dose?
9. Did the patient have a similar reaction to the drug or a related agent in the past?
10. Was the adverse event confirmed by any other objective evidence?
The actual ADR Probability Scale
form and instructions on how it is
completed are provided below. Total scores range from -4 to +13; the reaction is considered definite if the score is 9 or higher, probable if 5 to 8, possible if 1 to 4, and doubtful if 0
or less.
While this scale includes all of
the usual features that are important
in assessing causality, the scale is not weighted for the most critical elements in judging the likelihood of drug-induced liver injuries, such as
specific time to onset, criteria for the time of recovery, and list of critical diagnoses to exclude, making the scale of limited use in assessing hepatotoxicity. The Naranjo scale also relies upon testing for
drug levels, which is rarely helpful in idiosyncratic drug-induced liver disease. Finally,
the scale was designed for use in clinical trials,
and points are subtracted if the reaction
reappears with the administration of a placebo, which does not apply to the usual case of drug-induced liver disease. Direct comparisons to the RUCAM system have shown that the ADR Probability Scale is easier to apply, but has less sensitivity and specificity in assigning causality to cases of drug-induced liver injury.
According to the score Adverse Drug Reaction is categorized into four categories :
Total score:-
· >9 indicates definite ADR
· 5-8 indicates
probable ADR
· 1-4 indicates possible ADR
· 0 indicates
doubtful ADR
References :
https://www.google.com/url?sa=t&source=web&rct=j&url=https:// www.ncbi.nlm.nih.gov/books/NBK548069/&ved=2ahUKEwjN_- ST1bj8AhWD53MBHTGWAUcQFnoECB8QAQ&usg=AOvVaw00UiSs8U
2LCiRrnzxU5Qms
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