Rating Scales
The Naranjo Adverse Drug Reaction (ADR) Probability Scale is a tool used to assess causality between a medication and an adverse effect. There are several limitations that should be noted: “unknown” responses can limit the utility of the scale, the subjectivity and consistency of the observers of the adverse drug reaction, and it cannot be used in cases of overdose. The ADR Probability Scale consists of ten questions answered as “Yes,” “No,” or “Do Not Know” with corresponding point values assigned. The total score will categorize the adverse reaction as definite, probable, possible, or doubtful ADR.
| Question | Yes | No | Do Not Know | Score | |
|---|---|---|---|---|---|
| Total Score | 0 | ||||
Current Category
The reaction could be related to the medication, but other factors are more likely to be the cause.
Definite ADR
≥ 9 points
The reaction is almost certainly due to the medication.
Probable ADR
5–8 points
The reaction is likely due to the medication.
Possible ADR
1–4 points
The reaction could be related to the medication, but other factors are more likely to be the cause.
Doubtful ADR
≤ 0 point
The reaction is unlikely to be related to the medication.
Naranjo CA, Sellers EM, Sandor P, et al. A method for estimating the probability of adverse drug reactions. Clin Pharmacol Ther. 1981;30:239-45.
National Institute of Diabetes and Digestive and Kidney Diseases. (2012–). LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Center for Biotechnology Information.