Management of the low-grade abnormal Pap smear: What are women’s preferences?

Trained interviewers used a standardized approach to elicit preferences from each subject. Subjects were read a description of all the procedures involved in the scenarios. Descriptions were accompanied by cards summarizing each procedure in pictures and words, and included information about the possibility of progression and spontaneous regression of the Pap smear abnormality. Subjects were encouraged to ask questions at any point during the interview. Procedure descriptions are available from the authors on request.

TABLE 1

Clinical scenarios classified by management approach and required treatment^*

Standard gamble

Subjects were asked their preference between the certainty of the scenario under consideration and an uncertain prospect of either having cervical cancer treated by hysterectomy or full health. A probability wheel was used as visual aid.⁹ The probability of cervical cancer was altered until the subject was indifferent between the certain scenario and the uncertain prospect. Once all 6 scenarios had been scored, each subject was asked about her preference between the certainty of cervical cancer treated by hysterectomy and the uncertain prospect of immediate death or full health, using the same method.

At the end of the interview, both the subject and the interviewer completed evaluation forms including ratings of how well the subject understood the standard gamble rating exercises. Subject confusion was also defined a priori as those placing a higher utility on scenario 3 (observation for a long period followed by cone biopsy), which represented the longest period of uncertainty followed by the most invasive procedure, than on scenario 1 (a single mildly abnormal Pap smear evaluated by observation which then resolved spontaneously), which represented the absence of any invasive procedure.

Statistical analysis

Descriptive statistics were generated for ratings of each scenario for the entire group and with the confused subjects removed. Confused subjects included those who reported they found the interview “very confusing,” those who were recorded by the interviewer as finding the interview “very confusing,” and those whose rankings met the criteria for subject confusion, as described above. Means, standard deviations, medians, and percentiles were calculated for each scenario. The mean differences in adjusted standard gamble ratings between paired scenarios was evaluated using a t distribution. Multiple regression analyses were used to explore how much between-subject variation in the standard gamble scores was explained by the variables listed above.

A simple decision tree (Figure 1) was constructed to contrast preferences for an observational approach vs early colposcopy. Outcome probabilities were derived from meta-analyses of the medical literature,⁵ from observational data obtained at the same Northern California family planning clinics,¹⁰ and, for cone biopsy outcomes, from expert opinion obtained using a modified Delphi process.¹¹ Utilities were assigned to the decision tree based on the standard gamble results. Women having 2 consecutive low-grade abnormal Pap results followed by a normal Pap result were assigned the same utility value as that for women with a single abnormal result. Analysis of the tree, including 1-way and 2-way sensitivity analysis of key variables, was conducted with Data 3.5.

Results

One hundred seventy interviews were completed. Characteristics of the interview subjects are shown in Table 2. A total of 22 subjects were designated “confused.” Analyses including the confused subjects did not alter the pattern of results, but the range in responses was larger. All analyses are presented here with confused subjects removed (n = 148).

Median ratings with 25th–75th percentiles for the paired scenarios rated by the standard gamble are shown as box plots in Figure 2. Mean adjusted scores, standard deviations, and mean differences in scores between paired scenarios are shown in Table 3. Notable findings include the following. (1) For each scenario, the range of responses by either rating method was very large. (2) Mean differences in utilities for observation vs early colposcopy were small. (3) For the paired scenarios in which the outcome was spontaneous resolution, observation was preferred (P = .01); in the paired scenarios in which the outcome was cryotherapy, early colposcopy was preferred (P = .02). (4) In the multiple regression analyses for each scenario, age, education, ethnicity, religiosity, and having known someone with cervical cancer together explained only a small amount of the variability between subjects (range for R², .09–.22).