Introduction

Urogenital prolapse is a common, distressing condition for women, although, since there is no standard validated definition, it is difficult to determine prevalence in the female population. However, three large population studies suggest that the prevalence of stages 3–4 prolapse is in the range of 2–11% [1–3]. In addition, there is an 11% lifetime risk of needing surgical correction of urogenital prolapse with a third of these women requiring further surgery in the future [4].

There is often a dichotomy of opinion when comparing clinician's evaluation with that of patients; a large questionnaire-based study in the UK has demonstrated that clinicians tend to be more optimistic when evaluating the outcome of pelvic floor surgery than patients [5].

To address this difference of opinion, Quality of Life (QoL) assessment is considered to be essential in outcome evaluation following any intervention for urogenital prolapse. However, there are only a few validated questionnaires available which record both symptom distress and QoL in this population. The Pelvic Floor Distress Inventory and the Pelvic Floor Impact Questionnaire [6] address symptom distress and quality of life impact respectively in women with urogenital prolapse whereas the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire [7] evaluates sexual function in these women.

Although these QoL instruments are a vital part of outcome assessment, they are relatively long and require calculation of a score, making them difficult to use in a busy clinical setting. In contrast, global indices that ask a patient to rate the response of her condition to intervention (such as surgery in pelvic organ prolapse) are much more simple and easy to use, interpret and ultimately compare across different research settings. As suggested by Yalcin and Bump [8], the goal of a global scale is to gain an overall appraisal of a complex phenomenon, not to evaluate each of its component parts. Therefore, there may be uncertainty regarding precise aspects of improvement which results in an individual rating chosen by the patient [9]. However, a global index is completed by the patient and represents her own unique personal perception. This is in direct contrast to the total scores that can be calculated from multiple question condition specific QoL instruments, as these are derived from questions set by clinicians rather than patients themselves [10]. In addition, global indices have been shown to be precise when applied by the same person over time [9]. Previous studies have recommended the use of global indices as a unique reflection of individual patient perception [10].

Currently, there is no condition specific global instrument that has been developed or evaluated as an outcome assessment tool in pelvic organ prolapse research. The Patient Global Impression of Improvement (PGI-I) has been validated for use in female patients with urinary incontinence [8] (Table 1), but not in those with prolapse.

Table 1 PGI-I Scale in pelvic organ prolapse
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The aim of this study was to validate the use the PGI-I in women following surgical treatment of urogenital prolapse by correlating it with other outcome assessment measures such as objective assessment of prolapse, QoL assessment and patient satisfaction.

Materials and methods

This validation was part of a prospective longitudinal observational study. Women complaining of symptomatic urogenital prolapse, on the waiting list for pelvic floor reconstructive surgery were recruited from a tertiary referral urogynaecology centre.

All patients fully understood the nature and purpose of the study and written informed consent was obtained prior to study entry. Ethical approval for this study was obtained from the Kings College Hospital Ethics committee.

Women were pre operatively assessed objectively by clinical examination using the Pelvic Organ Prolapse Quantification System (POP-Q) [11]. They were then assigned an ordinal scale based on the degree of prolapse. Impact of urogenital prolapse on women's QoL was assessed with the Prolapse QoL questionnaire (PQoL). The PQoL is a reliable and validated questionnaire which assesses both the severity of symptoms of prolapse and their impact on the QoL of affected women. The scoring system of the PQoL has been previously reported [12].

Women were also asked to list up to five personal goals they hoped to achieve following surgery. At each post-operative review, they also completed a visual analogue scale (VAS) documenting the degree of goal fulfilment and this was used to determine subjective satisfaction. Finally, they also completed the PGI-I to indicate overall satisfaction with their post operative condition. Women were followed up at 6 weeks, 3 months, 6 months, and 1 year following surgery. At each follow-up visit, prolapse was objectively assessed with POP-Q and women also completed a PQoL, VAS for goal achievement and PGI-I.

We attempted to establish the construct validity of the PGI-I by correlating the final PGI-I response with other measures of response to prolapse surgery both objective and subjective, also measured at the 1 year follow-up visit:

  1. 1.

    Objective assessment of prolapse degree based on ordinal stage on POP-Q,

  2. 2.

    Change in domain and total scores on pQoL from baseline levels

  3. 3.

    VAS of patient goal achievement

The study was sized to give an 80% power to detect a correlation between two continuous variables of 0.25 at the 5% significance level.

Wilcoxon's signed rank test was used to compare pQoL results at baseline and at the one year follow-up, whilst the paired t test was used to compare POP-Q ordinal scores pre treatment and at one year. Cronbach's alpha test was used to determine test–retest reliability of the PGI-I using the 6-month and 1-year response in a cohort of women whose postoperative condition was determined to be unchanged during this period, based on POP-Q and VAS scores. Pearson's coefficient was used for correlations. Statistical analysis was performed with SPSS (V. 13).

Results

A total of 109 women completed the first year of this study. Mean age was 64.2 years (range, 42–85 years), mean parity was 2 (range, 1–4) and mean ordinal stage of prolapse was 2 (range, 1–4).

Objective assessment showed a statistically significant improvement in POP-Q scores at the 1 year visit (p < 0.01). Analysis of the pQoL questionnaire also showed a significant improvement from pre-operative scores at the 1-year visit, in both total scores as well as individual domain scores (p < 0.01).

There was excellent correlation between PGI-I scores and both objective and subjective measures used to determine treatment outcome at 1 year (Table 2). The scoring system on the POP-Q assessment and the pQoL scores are similar, in that a lower score on both equates with better health (ordinal score of zero on POP-Q = no prolapse, pQoL score of zero= no impact on QoL). Similarly, a low score on the PGI-I indicates an overall improvement in a woman's perception of her condition post-treatment. (PGI-I score of 1 or 2 = very much better and much better, respectively). There was significant positive correlation between PGI-I score and the objective assessment of prolapse on POP-Q system using ordinal and change in pQoL scores from baseline pre-operative levels (Figs. 1, 2, 3).

Table 2 Correlation of PGI-I with other outcome measures at 1 year
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Fig. 1
figure 1

Schematic representation of outcome measures

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Fig. 2
figure 2

Correlation of PGI-I with POP-Q

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Fig. 3
figure 3

Correlation of PGI-I with PQoL

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Conversely, patient goal achievement was documented on a simple VAS system where a high score equated with high achievement of goals and vice versa. This was reflected by a significant negative correlation between PGI-I and patient self-documentation of goal achievement (Fig. 4).

Fig. 4
figure 4

Correlation of PGI-I with patient achievement

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Cronbach's alpha was used to determine the internal consistency or average correlation of items in a survey instrument to gauge its reliability. Alpha coefficient ranges in value from 0 to 1 and the higher the score, the more reliable the generated scale is. A score ≥0.7 is generally considered as an acceptable reliability. The test–retest reliability of the PGI-I was found to be excellent based on Cronbach's alpha analysis of responses (0.849) at 6 months and 1 year.

Discussion

To the best of our knowledge, this is the first study that validates the use of the PGI-I as a global assessment index of response to surgical management of urogenital prolapse.

We have established the construct validity of this global assessment index for treatment response in prolapse management by showing that PGI-I responses correlate significantly with other outcome measures used in prolapse: change in degree of prolapse measured objectively by the POP-Q system, change in pQoL scores and VAS of patient goal achievement. In addition, we have also demonstrated the significant test–retest reliability of this index.

The PGI-I scale was originally modelled after psychopharmacological scales described in 1976 (Clinical Global Impression) [13] The Clinical Global Impression–Improvement scale (CGI-I) is a 7-point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of the intervention and rated as: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.

Clinical Global Impression—Improvement scales are widely used in psychiatry. They have also been used in several other fields in medicine. The Audiological Rehabilitation Clinical Global Impression [14] was developed to assess outcome following hearing aid fitting based on Clinical Global Impressions. Patient and Clinical Global Impression of Change have also been used to evaluate the efficacy, tolerability and safety of combination therapy in the management of neuropathic pain [15].

Previous work in the incontinent population by Yalcin and Bump established the construct validity of the PGI-I in female patients with stress urinary incontinence [8]. In their study, the stems of the questionnaire were altered for use in patients with lower urinary tract condition, whilst maintaining the response options. The PGI-I version used in our study is identical to the one validated for use in women with urinary incontinence.

We acknowledge that our study has some weaknesses. Our numbers are relatively small although we had complete data from all patients and the study had been powered by an independent statistician. Cronbach's alpha test was used to determine test–retest reliability of the PGI-I using the 6-month and 1-year response. Although this cohort of women were determined to have no changes in their postoperative condition during this period, based on POP-Q and VAS scores, there is potential for bias over responses separated by a 6-month period.

When considering outcome measures until relatively recently there has been a paucity of data regarding patient expectations following treatment for urogenital prolapse. Expectations regarding outcome are shaped by previous personal experiences, those of friends and relatives and also by the attitude and experience of the clinician. Consequently the concept of ‘cure’ is relative. Achieving anatomical restoration of the urogenital tract may not be regarded as a cure if new symptoms related to urinary, sexual and bowel dysfunction are experienced following surgery.

It has become increasingly obvious that women with urogenital prolapse seek treatment primarily to improve their QoL. A recent study by Jelovsek et al. showed that women with POP have a decreased body image and overall QoL [16]. Digesu et al. have also shown that women with symptomatic POP have significant reduction in QoL scores [17]. Improvement in QoL is seen as a powerful indicator of effective treatment although at present there is little evidence to clarify how QoL evaluation relates to patient expectations and what constitutes a significant or meaningful change [18]. Previous work in our unit has shown that QoL outcomes based on the physician's perspective may not be valid as physicians often underestimate patient's bother [19]. An alternative way of examining patient expectations of treatment is that of patient orientated goals [20]. Whilst long term follow-up studies have revealed that goal achievement is related to general QoL measures [21] there are limited data comparing these two measures of outcome and satisfaction.

The advantage of using a global index such as the PGI-I is that it provides the single best measure of significance of change from the individual perspective [22]. A global index can assess clinically meaningful change by taking into account more information that may affect health related QoL. It has the advantage that it is self administered thereby avoiding physician bias. It is also a single question assessment which makes it easy for the patient to fill in and is less time consuming than a more detailed multiple question condition specific QoL instrument. This in turn makes it an ideal instrument to be used in the clinical setting of a busy urogynaecology unit. From a research point of view, its versatility in terms of application in both urogenital prolapse and urinary incontinence and simplicity of usage should make it an ideal outcome assessment tool.

In essence, the PGI-I encompasses all outcome measures: objective, subjective, quality of life and patient-centred goals. It is simple, pragmatic and easy to use whilst being sensitive to change. It is a true reflection of “success” following surgery for urogenital prolapse as it reflects a woman's overall appraisal of her response to treatment.

Our study has shown that the PGI-I, previously validated in outcome studies of stress urinary incontinence can be applied in exactly the same way for women undergoing surgery and presumably other forms of management of urogenital prolapse. It is quite easy to understand and can be used in both clinical practice and in the research setting.

Consequently, this global index may be a valuable addition not only in clinical practice to evaluate response to prolapse treatment but also an outcome assessment tool in trials comparing interventions in the management of urogenital prolapse.