An Amateur's View of MQSA

1
An Amateur's View of MQSA

• Victor E. Anderson, C.H.P.
• Radiologic Health Branch
• California Department of Health Services

2
The Circle Problem

• Inspectors are required by eye to determine if a
  part is out of round, e.g., not a circle.
• Not a hard process, unless you define roundness.

3
Mammography

• Similar problem
• Is it a cancer or ?
• Some Factors
• Quality of image
• Skill of interpreter
• Size of tumor mass
• Physical/Psychological

4
Problem

• Screening test.
• Not expected to detect every tumor
• When does the interpreter and system fail?
• Easy answer does it meet MQSA Standards?
• What about false negatives and positives?

5
Facility Failure

• How bad is bad?
• Or How many cancers went undetected that
  should have been seen?
• Two interrelated areas
• Physical factors (Physics)
• Ability of the Interpreter

6
Review Actions

• How far back in time does the problem go?
• Previous inspections
• Clinical Image Reviews
• MQSA records
• Image Quality
• Interpreter skill (Additional Mammography Review)

7
How Many?

• Typically 30 additional cases.
• Breast Cancer Rate
• Various with age
• About 0.008 on the average per screening
• Out of 1,000 cases, eight may have detectable
  cancer!

8
Rates and Sampling

• Mammography facilities see lots of patients.
• As much as 20 per day per machine.
• About 100 per week per machine.
• A ten machine facility could find about eight
  cases per week.
• What is bad?

9
False Negative Rates
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False Negatives

• Indications are that
• For every eight
• About two will be missed.
• Given a poorly performing facility
• How many films to review?
• How bad is bad?

11
How Far Back?

• Ideally no further than last inspection.
• Indicators
• Daily checks
• Physics reports
• Referrals
• CIR
• AMR

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One Testing Solution

• Make a time estimate.
• Using average rates, determine number of cases
  seen.
• Total number of films.
• How big a sample?

13
Sample Size

• Mil spec tables or AQL
• Period of potential sub standard performance is
  10 weeks.
• Four machine facility.
• 4,000 patients.
• AQL table indicates 200 samples with an
  acceptance level of one false negative.
• And a rejection level of two false negatives.

14
Issues

• Cost of sample size.
• What is at stake?
• Rational assurance that proper screening
  occurred.
• Follow up

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Conclusions

• MQSA provides good QA/QC
• Need Sampling scheme to follow up.
• Provide rational basis for extent of a problem
  with respect to time.
• How many patients to notify?
• Aid in corrective actions.

16
References

• False-negative breast screening assessment what
  lessons can we learn?, Burrell HC, Evans AJ,
  Wilson AR, Pinder SE., Clin Radiol 2001
  May56(5)385-8
• Comparison of full-field digital mammography with
  screen-film mammography for cancer detection
  results of 4,945 paired examinations., Lewin JM,
  Hendrick RE, D'Orsi CJ, Isaacs PK, Moss LJ,
  Karellas A, Sisney GA, Kuni CC, Cutter GR.,
  Radiology 2001 Mar218(3)873-80
• The evaluation of false negative mammography from
  malignant and benign breast lesions., Wang J,
  Shih TT, Hsu JC, Li YW., Clin Imaging 2000
  Mar-Apr24(2)96-103