Lung cancer screening in the US and pack years

What does the USPSTF recommend?

Its final recommendation, published on 9 March 2021, is “annual screening for lung cancer with LDCT in adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years.” LDCT is a low-dose CT (computed tomography) scan.

All three conditions apply together:

• age 50 to 80
• a 20 pack-year smoking history
• smoking now, or having quit within the past 15 years

Screening stops once a person has not smoked for 15 years. The recommendation is graded B. When it was checked in October 2026, the USPSTF website showed no update in progress.

What changed from 2013?

The 2021 recommendation replaced the 2013 criteria. It lowered both the starting age and the pack-year figure:

At a steady number of cigarettes a day, this is how long it takes to reach each figure:

How are pack years used in the US criteria?

The pack-year figure is one of the three conditions, so applying the criteria needs a person’s smoking history as a number of pack years. A pack year is 20 cigarettes a day for one year. To work out pack years, multiply cigarettes a day by years smoked, divide by 20 and add up every period: see what is a pack year?

For a history that changed, each period counts. Someone who smoked 10 a day for 10 years and then 20 a day for 15 years has 10 × 10 ÷ 20 = 5 pack years plus 20 × 15 ÷ 20 = 15 pack years: 20 in all.

The calculator converts cigars, pipes, loose tobacco and other types into cigarettes using approximate figures, which the References page says are “not an exact science”. As far as we can find, the USPSTF recommendation does not say how cigars, pipes or other tobacco count towards its 20 pack years, so the calculator’s conversions for these types are this site’s own, not the USPSTF’s.

The criteria also depend on time since quitting. The calculator’s optional history step records whether someone still smokes and, if they have stopped, the year they stopped (and the month, if known). The clinician version adds this to its line for the record.

The site’s FAQs add a caution about pack years in general. FAQ 2 calls them “only a crude imprecise description of smoking related exposure”, and recommends recording years smoked as well: see pack years and years smoked.

Does the US recommendation apply in the UK?

No. It is a recommendation for the United States. In England, the Lung Cancer Screening Programme offers a lung health check to people aged 55 to 74 who have ever smoked, and decides who is scanned using a risk score from two risk models, not a pack-year figure. See lung cancer screening in England.

Where can I read the recommendation?

The full citation is: US Preventive Services Task Force; Krist AH, Davidson KW, Mangione CM, et al. Screening for lung cancer: US Preventive Services Task Force recommendation statement. JAMA 2021;325(10):962-70. The recommendation is on the USPSTF website.

For what the figure represents in cigarettes, see is 20 pack years a lot? Pack years are a record of past smoking, not a diagnosis. If you are worried about your health, speak to your GP practice or use NHS 111.