Comparison of benefit of interventions across primary care
| CATEGORY | ACUTE SYMPTOMS | LONG-TERM SYMPTOMATIC CONDITIONS | CVD (PRIMARY PREVENTION) | CANCER SCREENING (CANCER-SPECIFIC MORTALITY) | SOCIAL SCREENING OR HEALTH PROMOTION |
|---|---|---|---|---|---|
| Estimated benefit | NNT = about 5 | NNT = about 7 | NNT = about 40 over 5 years | NNS = about 1000 over 10 years | NNS = ∞ |
| Encounters with benefit per year | 176* to 720† | 143‡ to 617§ | 3.25‖ to 12¶ | 0.13# to 0.36** | 0 |
| Encounters with benefit over 30 years | 5280 to 21 600 | 4290 to 18 540 | 98 to 360 | 4 to 11 | 0 |
CVD—cardiovascular disease, NNS—number needed to screen, NNT—number needed to treat.
↵* Acute visits—conservative: Visits per year are based on 220 working days. Assuming 20 visits per day with 20% of visits having some acute symptom component, (220 × 20) × 0.2 = 880. Estimated NNT of 5 means 176 (880/5) encounters with benefit per year.
↵† Acute visits—better case: Visits per year are based on 240 working days. Assuming 30 visits per day with 50% of visits having some acute symptom component, (240 × 30) × 0.5 = 3600. Estimated NNT of 5 means 720 (3600/5) encounters with benefit per year. Assumptions minimizing benefit include no weekends, holidays, or evenings worked.
↵‡ Long-term symptomatic conditions—conservative: Based on a patient panel of 2000, assuming about 50% of patients have 1 continuing problem (note that some patients will have more and some will have none), then 2000 × 0.50 = 1000, with an NNT of 7 (1000/7 = about 143).
↵§ Long-term symptomatic conditions—better case: Visits per year are based on 240 working days. Assuming 30 visits per day with 60% of visits having some chronic symptom component, (240 × 30) × 0.6 = 4320. Estimated NNT of 7 means 617 (4320/7) encounters with benefit per year.
↵‖ Long-term CVD prevention—conservative: Using age 45 as the start of screening (knowing that is early) to age 75, that represents 32.5% of the population or 650 patients. Assuming all will be high enough risk to be offered at least 1 therapy, estimated NNT is 40 over 5 years (650/40 = 16.3 per 5 years, 16.3/5 = 3.25 per year).
↵¶ Long-term CVD prevention—better case: Using age 45 as the start of screening (knowing that is early) to age 75, assuming this demographic makes up 60% of the patient panel or 1200 patients, and assuming all patients will be high enough risk to be offered at least 1 therapy, with the most effective therapy (hypertension treatment), NNT is estimated to be 20 over 5 years (1200/20 = 60 per 5 years, 60/5 = 12 per year).
↵# Long-term cancer prevention—conservative: Assuming 650 eligible patients (as in CVD) and 2 maneuvers per patient, benefit would be 2 per 1000 over 10 years, or 1 in 500 over 10 years. So, we take 650/500 = 1.3 encounters with benefit over 10 years. That is 0.13 over 1 year or around 4 over 30 years.
↵** Long-term cancer prevention—better case: Using age 45 as the start of screening (knowing that is early) to age 75, assuming this demographic makes up 60% of the patient panel or 1200 patients, and assuming the best-case scenario (ie, mammography with NNS = 337 over 10 years), 1200/337 = 3.6 over 10 years. That is 0.36 over 1 year.