Naranjo algorithm

The Naranjo algorithm, Naranjo Scale, or Naranjo Nomogram is a questionnaire designed by Naranjo et al. for determining the likelihood of whether an ADR (adverse drug reaction) is actually due to the drug rather than the result of other factors. Probability is assigned via a score termed definite, probable, possible or doubtful. Values obtained from this algorithm are often used in peer reviews to verify the validity of author's conclusions regarding adverse drug reactions. It is also called the Naranjo Scale or Naranjo Score.

Several investigators, including researchers at the FDA, have developed such logical evaluation procedures, or algorithms, for evaluating the probability of an ADR.[6, 20-24] Almost all of these methods employ critical causation variables identified by Sir Austin Bradford Hill in 1965.[25] The most widely accepted of these instruments is the Naranjo algorithm[22] (Table). This method has been tested for internal validity with between-rater reliability testing, and its probability scale has consensual, content, and concurrent validity as well as ease of use.

Questionnaire

1. Are there previous conclusive reports on this reaction?

2. Did the adverse events appear after the suspected 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 appear when the drug was readministered?

5. Are there alternative causes that could have caused the reaction?

6. Did the reaction reappear when a placebo was given?

7. Was the drug detected in any body fluid in toxic concentrations?

8. Was the reaction more severe when the dose was increased, or less severe when the dose was decreased?

9. Did the patient have a similar reaction to the same or similar drugs in any previous exposure?

10. Was the adverse event confirmed by any objective evidence?

Scoring

≥ 9 = definite ADR
5-8 = probable ADR
1-4 = possible ADR
0 = doubtful ADR

References

Naranjo CA; Sellers EM; Sandor, P; et al. (1981). "A method for estimating the probability of adverse drug reactions". Clin. Pharmacol. Ther. 30 (2): 239–45. doi:10.1038/clpt.1981.154. PMID 7249508. {{cite journal}}: Cite has empty unknown parameter: |1= (help); Missing |author2= (help); Unknown parameter |name-list-format= ignored (|name-list-style= suggested) (help)

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