Recent Trends in Followup and Surveillance on Medicare Beneficiaries

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Recent Trends in Follow-up and Surveillance on
Medicare Beneficiaries

• Todd Anderson
• Congressional Budget Office
• January 26, 2004

The views expressed in this talk are those of
the author and should not be interpreted as those
of the Congressional Budget Office.
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Questions

• Frequency of colonoscopy in the years following
  index polypectomy.
• Patterns of short-term follow-up following
  sigmoidoscopy.

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Data

• Longitudinal 5 random sample of Medicare claims
  data, beneficiary level and monthly, from
  1989-1999.
• Newly eligible beneficiaries are added to sample
  each month to maintain representative panel in
  each year.
• Fee-for-service Beneficiaries only, 10 to 15
  percent of beneficiaries enrolled in managed care
  are excluded.
• Final Sample Size 3.4 million unique
  individuals (1.6-1.7 million beneficiaries per
  year).

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Colonoscopy frequency following a
PolypectomyMethodology

• Starting in 1994 (but allowing for later entry
  for new enrollees), each beneficiary is included
  in sample until
• -- Death
• -- Initial disenrollment from FFS, or
• -- End of 1999 (sample size2.4 million).
• Selected all who had a colonoscopy or
  sigmoidoscopy with polypectomy (sample
  size125,000) -- Upper Bound
• Identified month of first colonoscopy at least 6
  months after polypectomy
• Dropped those with any cancer-related diagnosis
  code in two different months between 1991 and
  1999 -- excluding about 65,000 beneficiaries --
  Lower Bound

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Limitations

• Analytic treatment of potential cancer
  beneficiaries too undifferentiated
• Cannot distinguish among types or size of polyps
  removed
• Sample attrition correlated with health status
• Cant differentiate between screening and
  non-screening triggering events.

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Follow-up after sigmoidoscopyMethodology

• From individuals in 1993-1999 sample, selected
  those with fewer than two months in which a
  Cancer diagnosis was assigned between 1991 and
  1999
• Defined triggering event as a sigmoidoscopy in an
  individual with at least 12 months of FFS
  enrollment history AND no sigmoidoscopy or
  colonoscopy in the previous six months
• Further excluded individuals with barium enema in
  previous six months OR in month of triggering
  event, or those without six months of FFS
  enrollment after the month of the triggering
  event
• Sample size 83,198 sigmoidoscopies
• Identified all polypectomies in the month of the
  triggering event or in subsequent six months
  (6,257 cases). Further identified
  sigmoidoscopies with polypectomy in the initial
  service (1,218 cases).

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Limitations

• Cannot differentiate among types or sizes of
  polyps removed
• Cannot differentiate between screening and
  non-screening triggering events

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Key Findings

• 55 to 64 of Medicare beneficiaries having a
  colonoscopy or sigmoidoscopy with polypectomy
  obtained at least one surveillance colonoscopy in
  a 5-year period
• A large majority of Medicare beneficiaries who
  underwent polypectomy within six months of a
  sigmoidoscopy had polyps removed in subsequent
  procedures