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Oppdatert februar 2003
Decision Making in General Practice
Women’s Health
Early Diagnosis – Preventive Treatment
Answers
Vignette 1
 A gynaecological examination is not necessary at this point.
 Chlamydia test and cervical cytology will be evaluated as tests to be taken.
 The reason for doubt/hesitation is due to the high risk for false positives.
Vignette 2
 These types of tests aren’t as necessary as they were in the previous 20 years.
Incidence of cervix dysplasia and cancer in the 50s is clearly decreasing. It would
probably be wise for a Pap smear to be taken in a few years. She should be
informed that she should contact her doctor immediately if she notices any signs
of vaginal bleeding.
 Dysplasia among younger women is usually a false positive test result. It is
recommended to wait until the age of 25 years to start with regular cytologic
controls.
Chlamydia screening
Prevalence 10%
+
-
Test
Chlamydia infection
+
95
18
5
882
100
900
How many test results are false positives?
113
887
1000
18
How likely is it that a positive test result is due to infection (percentage)? 84%
Prevalence 0.5%
Test
+
-
Chlamydia infection
+
4
20
1
975
5
995
Klinisk beslutningslære, svar til kvinnemedisin, kurs 6, Terje Johannessen
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976
1000
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Oppdatert februar 2003
How many of the test results are false positives?
20
What percentage of positive test results is due to infection? 16%
What do you say to a 30 year old woman who you routinely give Chlamydia tests and
the test results are positive?
When the likelihood of finding something wrong (in this case Chlamydia) is so low,
the test shouldn’t be taken. If the test is taken and is positive, then the patient should
be informed that the chances are very good that it is a false positive.
Vignette 2 continued
 You should discuss it with her now – patients expect that you inform them of any
findings. In the letter you should explain that even though the results have shown
cell changes, these are modest and most likely are not serious, but that the changes
should be followed-up. Such a message one year later could be more frightening.
On the other hand, the patient would be spared from thinking about the test results
were you not to inform her...
 The chance that it is a false positive result is high
 There is little chance that the reported changes have any prognostic value.
 Sources of error: abnormal cells did not exfoliate, improper sample taking,
inadequate material preparation, inaccurate interpretation of cellular changes.
Requirements for cervical cytology
Cytological laboratories use criteria that give high sensitivity (approx. 80%) and low
specificity. This is why there are a large number of false positive test results. A
positive test result indicates a defined probability that there is dysplasia; a negative
test result indicates little probability of dysplasia.
Dysplasia
cytology
+
-
Dysplasia histology
+
80
450
20
450
100
900
530
470
1000
How do you interpret a positive cytology from this?
Using high sensitivity and low specificity means that a high percentage of the positive
test results will be false positives (PPV = 25%) because the prevalence is low. Notice
that 20% of those with dysplasia were missed.
Early diagnosis
The disease
 the disease should be serious enough to merit screening
 should have a long lead time so that it can be detected
 early diagnosis must give better outcome for the disease
 health care services must have the time and resources to care for those whose test
results are positive
Klinisk beslutningslære, svar til kvinnemedisin, kurs 6, Terje Johannessen
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Oppdatert februar 2003

the treatment and follow-up must be set up so that the patient follows the
recommendations
The screening test
 must have an acceptable validity
 what percentage is false positive and what consequences are there for this
 must have little risk and not put a strain on the person taking the test
The screening programme
 low costs
 acceptable to the general public
 should be able to be integrated in the existing health care system
Breast cancer
Mammography
+
-
Confirmed breast cancer diagnosis
+
450
4.975
5.425
50
94.525
94.575
500
99.500
100.000
How many with breast cancer will go undetected? 50
How many with pathological findings tested by mammography do not have breast
cancer?
4.975
What is the probability that a positive mammography is due to breast cancer?
450/5.425=8%
Weigh the advantages and disadvantages of mammography screening against each
other.
The advantage is that most women with cancer will be detected. The disadvantage is
the considerable number of false positives. False positives use/waste resources and
cause alarm and worry in the recipient. To defend the use of screening the female
population for breast cancer there must be documented advantages such as survival
due to early diagnosis.
Vignette 3
Factors of HRT
 short term treatment – the woman’s preference
 long term treatment - total risk evaluation - cardiovascular, osteoporosis –
disadvantages are side effects, bleeding, daily use of medicine, need for regular
check-ups, need for endometrial monitoring (?).
Why combination therapy?
Klinisk beslutningslære, svar til kvinnemedisin, kurs 6, Terje Johannessen
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Oppdatert februar 2003
Endometrial cancer
Oestrogen alone therapy can be taken after a hysterectomy.
Vignette 3 continued
Absolute risk for uterine cancer:
Oestrogen alone therapy – 2.6% x 8.2 = 22%
Combination therapy – 2.6 %
Absolute risk for breast cancer:
Oestrogen alone therapy - 10% x 1.3 = 13%
Combination therapy - 10% x 1.5 = 15%
Advising a woman in her 50s
Life quality effects – mucous membrane of the urogenital tract, vegetative symptoms
during climacteric, “aging effects” (aging is not a disease)
Long term effects – positive outweigh the negative?
Negative
- breast cancer?
- overuse of medication, check-ups, patient role
Positive
- cardiovascular – evaluate total risk
- osteoporosis
- quality of life
Vignette 4
Osteoporosis – There is no basis for recommending general screening
Identify patients with clinical risk for osteoporosis:
 Weight/height - low BMI
 Smoking
 Early menopause
 Little exercise
 Genetics
 Previous fractures
 Tendency to fall
 Alcohol abuse and other factors that promote secondary osteoporosis
It is not possible to calculate a precise risk score.
Methods
X-ray of lower thoracic and lumbar spine
Measure bone mass density - DXA technique, measure hip and lumbar spine
Klinisk beslutningslære, svar til kvinnemedisin, kurs 6, Terje Johannessen
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