Compelling or irrelevant? Using number needed to treat can help decide

• Published in: Acta Psychiatrica Scandinavica Vol. 117; no. 6; pp. 412 - 419
• Main Author: Citrome, L.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2008; Blackwell
• Subjects: Antidepressive Agents - adverse effects; Antidepressive Agents - therapeutic use; Antimanic Agents - adverse effects; Antimanic Agents - therapeutic use; Antipsychotic Agents - adverse effects; Antipsychotic Agents - therapeutic use; Biological and medical sciences; Bipolar Disorder - drug therapy; Clinical outcomes; Clinical trials; Data Interpretation, Statistical; Depressive Disorder, Major - drug therapy; Dibenzothiazepines - adverse effects; Dibenzothiazepines - therapeutic use; Duloxetine Hydrochloride; evidence-based medicine; Evidence-Based Medicine - statistics & numerical data; Humans; Measurement techniques; Medical sciences; Methodology. Experimentation; number needed to treat; Outcome Assessment (Health Care) - statistics & numerical data; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Quetiapine Fumarate; Randomized Controlled Trials as Topic - statistics & numerical data; Research methodology; Schizophrenia - drug therapy; Secondary Prevention; Techniques and methods; Thiophenes - therapeutic use; Treatment Outcome; Mood disorder; Human; Evaluation; Methodology; Numbers needed to treat; Decision making; Treatment efficiency; Evidence-based practice; Schizophrenia; Depression; Bipolar disorder; Review; Evidence-based medicine; Recommendation; Psychosis; Statistical method; Treatment; Clinical trial; clinical trials; number needed to treat
• ISSN: 0001-690X; 1600-0447; 1600-0447; 0065-1591
• DOI: 10.1111/j.1600-0447.2008.01194.x

Objective:  The metric of number needed to treat (NNT), defined as the number of patients who need to be treated to achieve one additional favorable outcome, can help clinicians appraise claims that one intervention is meaningfully superior to the other. Method:  A review of the use of NNT to evaluate the differences between interventions in the treatment of depression, schizophrenia and bipolar disorder. Instead of using disparate measures such as point change on a rating scale, kilograms gained over time or relative differences, results can be converted into a common unit of measure –‘patient units’– so that the clinician can anticipate how often actual differences between interventions would be expected to be observed. Calculation of NNT is demonstrated using reports published in the psychiatric literature, together with different graphical techniques to display this. Results:  Clinical trial results expressed as NNT can be easily summarized and communicated effectively to patients, their families and payers. Limitations include ensuring that the NNT metric is calculated from well‐designed and well‐conducted research that enrolls subjects similar to patients that one treats in actual clinical practice, with doses of medications similar to what is used in the ‘real world’. Direct calculation of NNT is limited to binary or dichotomous outcomes. Conclusion:  Using NNT can help predict treatment response in terms of both efficacy and tolerability.