A 50-year-old man asks about starting a statin to treat his LDL of 130 mg/dL. He has no family history of coronary artery or cerebrovascular disease. He does not smoke, has a normal blood pressure, and is a competitive runner. The patient is especially concerned about the possibility of developing musculoskeletal symptoms that would impact his running. He has read extensively on the subject and specifically requests help in interpreting some studies. In one study, none of 5000 controls and 250 of 5000 statin-treated individuals developed musculoskeletal symptoms. He asks how many patients need to be treated for 1 patient to have musculoskeletal symptoms.
What is the number needed to harm in this study?

Question

A 50-year-old man asks about starting a statin to treat his LDL of 130 mg/dL.  He has no family history of coronary artery or cerebrovascular disease.  He does not smoke, has a normal blood pressure, and is a competitive runner.  The patient is especially concerned about the possibility of developing musculoskeletal symptoms that would impact his running.  He has read extensively on the subject and specifically requests help in interpreting some studies.  In one study, none of 5000 controls and 250 of 5000 statin-treated individuals developed musculoskeletal symptoms.  He asks how many patients need to be treated for 1 patient to have musculoskeletal symptoms.
What is the number needed to harm in this study?

Quizplus · Accepted Answer

There are several ways of expressing the magnitude of beneficial and harmful effects of treatments. These include the absolute and relative risk reduction and the odds ratio. Additional ways of expressing benefit and harm are the number needed to treat (NNT) and the number needed to harm (NNH). Because of their intuitive nature, the NNT and NNH have become increasingly popular ways to express clinical benefit and harm and to possibly compare modalities of treatment. The NNT and NNH are calculated in a similar fashion. The NNT is the reciprocal of the absolute risk reduction (the absolute event rate for control minus the absolute event rate for treated patients) when control and treated patients are compared. The NNH is the reciprocal of the absolute increase in adverse events (the absolute adverse event rate for treated patients minus the absolute adverse event rate for control patients) when control and treated patients are compared. In the study, the absolute rate of musculoskeletal symptoms (the adverse event rate of interest) in control patients is 0 and in statin-treated patients is 250 divided by 5000, or 5%. For the NNH, the reciprocal of differences between treated patients and controls is 1 divided by 5% minus 0%, or 20. Educational objective: The number needed to harm is the reciprocal of the difference between the absolute event rate in treated and control patients and provides a measure to assess the magnitude of potential harm from treatment. __________ References: Number needed to treat to benefit and to harm for intravenous tissue plasminogen activator therapy in the 3-4.5 hour window: joint outcome table analysis of the ECASS 3 trial. (http://www.ncbi.nlm.nih.gov/pubmed/19498197) Number needed to treat and number needed to harm with paliperidone palmitate relative to long-acting haloperidol, bromperidol and fluphenazine decanoate for treatment of patients with schizophrenia. (http://www.ncbi.nlm.nih.gov/pubmed/21552311)

A 50-Year-Old Man Asks About Starting a Statin to Treat