A 46-year-old woman comes to the office due to persistent joint pains. She has a history of rheumatoid arthritis and, for the past 6 months, has been on methotrexate (Mtx) therapy. However, her symptoms have shown little improvement. She has morning stiffness that lasts for >1 hour, and her erythrocyte sedimentation rate is 40 mm/hr. A discussion is initiated regarding modifying her therapy to include either subcutaneous (SC) tocilizumab (TCZ_SC) or SC abatacept (ABT_SC) in addition to Mtx. The patient expressed wanting to attempt the most effective treatment and avoid having to modify her treatment again.
Based on the study results, compared to Mtx therapy alone, what is the approximate number needed to treat over 1 year to prevent 1 additional clinical response of <70% improvement with (ABT_SC + Mtx) and (TCZ_SC + Mtx) ?

Question

Quizplus · Accepted Answer

Explanation: The number needed to treat (NNT) represents the number of patients who need to be treated (eg, with tocilizumab [TCZ] or abatacept [ABT] in addition to methotrexate [Mtx], as compared to Mtx alone) to prevent 1 additional bad outcome (eg, <70% improvement based on the American College of Rheumatology Criteria), assuming the treatment is beneficial. NNT is the inverse of the absolute risk reduction (ARR), or (1 / ARR). inverse of the absolute risk reduction (ARR) ARR is calculated by subtracting the experimental event rate (EER) from the control event rate (CER): ARR = CER − EER CER is the proportion of patients on Mtx alone (control group) who achieve <70% improvement: CER = 100% − 4% = 96% = 0.96. EER for (ABT_sc + Mtx) is the proportion of patients who achieve <70% improvement: 100% − 14% = 86% = 0.86. EER for (TCZ _sc + Mtx) is the proportion of patients who achieve <70% improvement: 100% − 29% = 71% = 0.71. Then, ARRs can be calculated as follows: ARR (Mtx versus [ABT_sc + Mtx]) = 0.96 − 0.86 = 0.10 _sc ARR (Mtx versus [TCZ _sc + Mtx]) = 0.96 − 0.71 = 0.25 _sc NNTs are obtained by calculating the inverse of ARRs: NNT (Mtx versus [ABT_sc + Mtx]) = (1 / ARR) = (1 / 0.10) = 10 _sc NNT (Mtx versus [TCZ _sc + Mtx]) = (1 / ARR) = (1 / 0.25) = 4 _sc Therefore, 10 patients would have to be treated with (ABT_sc + Mtx) to prevent 1 additional patient not achieving ≥70% improvement, whereas only 4 patients would have to be treated with (TCZ _sc + Mtx) to achieve the same outcome. _sc _sc Educational objective: The number needed to treat (NNT) is the number of patients who need to be treated to prevent 1 additional negative event in a period of time. NNT is a useful measure to evaluate the efficacy of a given therapy. NNT values for the same treatment will vary depending on the outcome, the period of observation, and the comparison group used.

A 46-Year-Old Woman Comes to the Office Due to Persistent