Agreement between patient reported outcomes and clinical reports after radical prostatectomy - a prospective longitudinal study

In clinical research information can be retrieved through various sources. Three commonly used sources of information are the patient themselves (self-reported), professional caregivers (clinical reports) and medical records. The preferred source depends on the specific research objective and the kind of information retrieved from the different sources. However, there may be different sources of information to choose from for several types of data such as morbidity, symptoms and health care utilization [1].

Medical conditions are commonly assessed retrospectively through patient interviews or patient charts [2–7]. When assessing outcomes after cancer surgery, documenting patient’s comorbidity is crucial as it may influence outcomes [8], such as recurrence [9], symptoms, complications [10] and bodily dysfunctions [11]. Another aim is documentation of health care utilization [12, 13]. Whereas studies comparing self-reported questionnaires with medical records are common [3, 6, 14–17], evaluation of clinical reports has received less attention [2, 6, 8].

Knowledge of quality characteristics such as agreement and reliability of different sources of information is important. Evaluating agreement between different sources contributes to the choice of source for information in clinical research. The focus in this study is on the agreement between patient questionnaires and case report form in a study of patients after radical prostatectomy. Assessing agreement by a single measure is often insufficient [18]. The use of measures of agreement for continuous outcomes was explored in a systematic review [19]. For categorical outcomes where data is classified according to concordant (positive/positive or negative/negative) and discordant (positive/negative or negative/positive) pairs, any recent systematic review is to our knowledge currently not available. However, according to Wongpakaran [20] and by our current review of the literature, many studies only report Cohen’s Kappa [21], sometimes combined with positive and negative agreement [18]. Kappa is a measure of the level of agreement in excess of chance, expressed as the relative difference in proportions of concordant pairs between observed and what would have occurred by chance. Positive and negative agreement estimates the conditional probability that, given that one of randomly selected rater makes a positive and negative rating, respectively, the other rater will also do so. A limitation with kappa is its dependence on the underlying prevalence, giving rise to for example low kappa values despite high percentage of agreement [18, 22]. This originates from how chance agreement is computed [23]. Gwet [24] proposed a statistic, named AC1, which is similar to kappa but use an estimator of chance agreement that is less dependent on the prevalence [20]. In the correction for chance agreement of kappa, it is assumed that all observed ratings may potentially agree by pure chance. In Gwet’s AC1, the likelihood of chance agreement is instead related to the proportion of ratings that may lead to an agreement. This portion does in turn depend on the observed marginal prevalence’s. This enables Gwet’s AC1 to avoid the problem of over or under correction that Kappa suffer from.

Agreement can be analyzed by generalized linear models for contingency tables [25]. Log-linear models are a class of models which to enable to quantify the contribution of row, column and diagonal effects as well as covariates on the outcome. The quasi-independence model [26] enables a greater degree flexibility and a more in-depth study of the structure of agreement than simple summary measures. For the situation where a source provides the true conditions (positive/negative), referred to as gold standard, the sensitivity and specificity of the different sources can be evaluated. Sensitivity and specificity measures the rate of cases being correctly classified as positive and negative, respectively.

The aim of this study was to evaluate the agreement between patient questionnaires and clinical reports in a study of patients after radical prostatectomy and to study patient characteristics associated with agreement between these two data sources.

Laparoscopic Prostatectomy Robot Open (LAPPRO) is an ongoing open, controlled and non-randomized prospective longitudinal trial comparing open retropubic and robot-assisted laparoscopic radical prostatectomy for localized prostate cancer at 14 centers in Sweden. The trial has been previously described in detail [27]. Patient scheduled for prostatectomy at the participating centers fulfilling the inclusion criteria (informed consent, age < 75 yr., ability to read and write Swedish, tumour stage cT1, cT2, or cT3 (TNM Classification of Malignant Tumors, [28]) with no signs of distant metastases, and a prostate-specific antigen level of < 20 ng/ml) were included.

Information was collected at 6–12 weeks, 12 and 24 months postoperatively both from case report forms by study personnel (either the operating urologist or clinical nurses) and from questionnaires filled out by the patients with regard to the following five outcomes: 1. swelling of groin or lower extremities, 2. complications and re-admissions, 3. re-operations, 4. added pharmacological therapy after surgery or due to local or distant recurrence and 5. local recurrence and metastases, see Fig. 1.

The questionnaires were based on concepts introduced in previous research projects [11, 29] and were content validated by experts in the field of urology and then face validated face with patients with prostate cancer. The case report forms were face validated with professional caregivers. The case report forms and questionnaires were further tested in a pilot study, after which final revisions were made [27]. The different questions in the case report forms and the questionnaires are presented in Supplement 1.

This study indicates that in a clinical trial, patients in general report a higher frequency of events than professional caregivers do. In the current study of patients after radical prostatectomy, with the exception of tumor recurrence, the incidence of various postoperative symptoms or events after radical prostatectomy for prostate cancer was consistently more frequently reported by the patients than in clinical reports. Missing information was consistently higher in the case report forms and increased at later follow-up.

Positive agreement was consistently lower than negative agreement for all the outcome variables. This is probably due to the relatively low incidence estimates and the large discrepancies in estimates between the patient and the clinical reports. Whereas both kappa and the odds of agreement varied across a wide range across the different variables and time points, despite other data characteristics of agreement being relatively similar, Gwet’s AC1 was relatively stable, which confirm previous findings [20, 24].

Accuracy and agreement between the different modes depends on what information is being collected [8]. For symptoms as well as events such as readmissions, an advantage with the questionnaire is that data is collected directly from the patient it concerns. However, the accuracy of recall may be questionable, especially in a retrospective setting with a long recall period [1]. Patients are more likely to recall a disease requiring a surgical or intensive pathologic/laboratory diagnostic procedure than a disease without such a procedures [14]. The time elapsed since the illness occurred and the seriousness of the disease influence agreement [3]. Diabetes has generally high agreement whereas chronic obstructive pulmonary disease and diseases with less explicit diagnostic criteria have poor agreement [6, 15]. For medical records recall bias is less of an issue as information is generally prospectively documented during a hospital admission that is data is recorded instantaneously in the course of time. A major limitation is that medical records may not cover the necessary information relevant for specific research objectives and underestimate symptoms based conditions [35]. They may also lack coverage as they miss patients not seeking health care or patients seeking health care in another county, or due to differences in reporting inpatient and outpatient visits [36]. An advantage with clinical reports is that they can be fit for purpose as opposed to medical records. A drawback is that information is filtered through the physician [11]. In the collection of signs, different types of medical examinations by an experienced clinician may be the only viable option.

The patient may be less prone to report complications when the clinical personnel asks for information compared with when he or she completes an anonymous questionnaire at home [37]. In this trial questionnaires were sent out and returned to a third party, the trial secretariat and not to the hospital/department where surgery was performed [27]. The information documented in the clinical record form was collected when clinical personnel met the patient during the follow-up meetings as well as from medical records. This probably explains the observed high agreement between the clinical record forms and the patient registry. A higher agreement between patient reports and medical records compared with patient reports versus physician reports has also been observed [8].

It has been found that patients with prostate cancer reported a higher incidence of symptoms such as fatigue compared to their physicians [38, 39]. A similar pattern was found in [40] but with a higher degree of agreement. Several study design features may contribute to these differences as discussed in [40].

Several of the studies ([5, 6, 9, 14, 16]) have used medical records as the gold standard enabling assessment of sensitivity and specificity. However, it may be an invalid assumption for other settings [35]. For the scenario where the Patient registry was regarded as the gold standard in reporting readmissions, the case report forms had a higher agreement and specificity compared to the questionnaire, whereas the questionnaire had a slightly higher sensitivity.

In our study some patient characteristics were found to be associated with agreement such as age, socioeconomic factors and depressed mood, which confirmed previous results [7, 13, 16]. Younger patients, who had no self-reported impairment in quality of life, depressed mood or negative intrusive thoughts, appear to report symptoms events more in agreement with those reported by clinical personnel. However, the association with medication (sleeping pills and/or tranquilizers) has not been previously reported as far as we know.

At later follow ups (12 and 24 months) the compliance in submitting clinical record forms was significantly lower compared with compliance regarding patient reports. One reason for this could be that part of the cohort was referred for surgery to a department of urology some, or even a long, distance from their home. This would be expected to result in a lower surgeon-patient physical follow-up (out-patients visit). Other contributing explanations could be that after 12 or 24 months the follow-up was not always by the operating urologist, and thus completion of the CRF may have been missed.

This study has both strengths and limitations. Strengths include the large study cohort, the longitudinal design, a high compliance of patients and the use of validated questionnaires [27]. Limitations include a lack of information of the specific personnel who completed the case report forms at the different visits and on the specific time periods the case report forms and questionnaires covered. Difficulties in being able to account for the longitudinal structure in the statistical model must be regarded as a limitation.

The differences in incidence and agreement across the different variables and time points highlight the importance of carefully assessing which source of information to use in clinical research. This study confirms the importance of using several measures to assess the degree of agreement between the sources. The previously reported benefits of Gwet’s AC1 are confirmed and researchers should be encouraged to consider this method. In clinical research, much effort is often devoted to increasing patient response rates. However, preventing missing data in clinical reports also needs further attention. Long-term follow-up should make use of patient reports, as clinical record forms tend to be missed by the health care. As different patient characteristics were found to increase agreement, such background information is relevant for the choice of data collection procedure.