Evidence-Based Practice for Nurses

then 70% of the women in this age group who screened positive for breast cancer
during mammography actually have breast cancer. Therefore, mammography
is better at detecting breast cancer in older women than in younger women.

It is important to ascertain the psychological and financial costs to the popula-
tion for the consequences of false-negative and false-positive screening results.
False-negative screening results can lead to further progression of disease without
treatment until symptoms become more apparent or the patient is rescreened.
False-positive screening results have psychological effects as well as potential
medical risks and inherent financial costs associated with further diagnostic
assessment because individuals are receiving follow-up care for diseases they
do not have. As a result, decisions must be made when establishing guidelines
for positive and negative results in screenings. These decisions are based on
the perceived costs of false-positive or false-negative screening test results.

Indicate whether the following statements are true or false.

1. Screenings are done even when there is no treatment for the disease being screened.


2. Sensitivity describes the ability of the test to correctly identify people without the disease
   by negative results.


3. As sensitivity of a test increases, specificity of the test decreases.


4. A false positive is when individuals are told they have the disease when in reality they
   do not.

TEST YOUR KNOWLEDGE 8-7

How did you do? 1. F; 2. F; 3. T; 4. T

Suppose you were told that your stool smear for occult blood was positive. The physician orders

a colonoscopy for you. After the procedure, you are told that your colon is healthy and that the

smear must have produced a false-positive result. How would you feel about this situation?

CRITICAL THINKING EXERCISE 8-3

8.8 Evaluating Health Outcomes and Services

By the end of this section, you will be able to:

‹Describe the use of epidemiologic designs in evaluating health outcomes and health

services in evidence-based practice

8.8 Evaluating Health Outcomes and Services 215