Chronic pelvic pain (CPP) is characterised by persistent pain or recurrent episodes of abdominal/pelvic pain [1] in men or women. CPP affects up to one out of ten men [2] and is associated with significant individual and socioeconomic impact [3], and yet it is understudied relative to female pelvic pain. Multiple pathophysiological mechanisms of CPP have been suggested which has led to the proposal of many classification systems to guide investigations of interventions and healthcare decisions. Some of the systems are widely accepted and used for research and/or clinical purposes whereas others are relatively unknown. There is a need to systematically review the classification systems used for CPP in men and to assess their value in guiding decision-making in the treatment of CPP. This step is critical as two recent Cochrane Reviews (which pooled data from more than 100 randomised controlled trials) concluded that there is still uncertainty regarding the efficacy of interventions for chronic prostatitis/chronic pelvic pain syndrome. Findings could inform whether current systems are adequate or whether we need to rethink the classification of CPP in men to improve management. The aim of this systematic review was to identify the systems that have been proposed to classify CPP in men, and to describe the characteristics of the systems and approaches used to develop them.

Terms relating to CPP in men and classifications systems were used to search the following databases: MEDLINE (including AMED, CINAHL, and PsycINFO), Scopus (including EMBASE and MEDLINE), and Web of Science. A classification system was defined as any system classifying CPP in men into at least two categories/domains, either as a complete classification system or as a part of a broader classification system.

Predefined eligibility criteria included publications in English or French, either proposing a classification system or providing additional information of a proposed classification system (e.g., addition or removal of categories/domains, or assessment tools/outcome measures). Classification systems of CPP in women only were excluded. Any type of publication was considered. If a classification system or the additional information of a proposed classification system was presented in more than one publication, only the first publication was included unless a later publication was meant to replace a previous publication (e.g., update or revision of a classification system by the same developers).

Two researchers independently screened all publications, starting with a title and abstract screening, followed by a full text screening. Two researchers independently extracted information from included publications and assessed the appropriateness and quality of development process of each classification system according to an adapted version of the Critical Appraisal of Classification Systems (Buchbinder et al., 1996). Discrepancies regarding eligibility, data extraction, and quality assessment were resolved by consensus or by consultation with another researcher.

A total of 9376 publications were screened. From these, 165 publications were considered at the stage of full text screening. Among these, 132 publications were excluded, with the majority excluded as they did not propose a classification system or provide additional information to a classification system that was already included (e.g., publications of the same developers presenting the same information). A total of 33 publications were included, of which 21 classification systems were proposed, with 12 publications presenting refinements or adaptations.

Figure 1 shows the 21 classification systems along with the development approaches used (i.e., approaches used to determine the categories/domains). Classification systems either proposed to classify a specific CPP condition into subtypes, characterise features of CPP (e.g., mechanisms, signs and symptoms, investigations, or imaging), or classify patients with CPP into subgroups. The most frequently classified specific CPP condition in men was chronic prostatitis/chronic pelvic pain syndrome and interstitial cystitis/bladder pain syndrome. Most classification systems either included anatomopathological, mechanistic, or sign- and symptom-features. Development approaches varied - most classification systems have relied on a judgemental approach. The scores reflecting the appropriateness and quality of development process of classification systems ranged from low to moderate values. Frequently unmet criteria included the lack or the absence of a combination of methods to propose a classification system, multidisciplinary faculty and/or patient engagement, combination of features or types of data, precision in assessment tools/outcome measures along with their evidence-based cut-off scores or thresholds. Some systems did not consider sex or gender differences, and it was unclear whether some systems can guide investigations of interventions and healthcare decisions.

Findings support the importance of assessing each classification system to carefully select the system that aligns with the intended purpose of use. Future classification systems might benefit from expansion beyond an organ-specific perspective of CPP in men. Determining which features are most relevant to CPP in men and examining the psychometric properties of the assessment tools/outcome measures used to classify CPP in men would be important to make recommendations. For classification systems derived from a judgemental approach, there is a need to validate the classification systems with patient-generated data. For classification systems derived from a statistical approach, there is a need to provide direction as to how results can be operationalised in research and clinical practice. Future studies should consider engagement with multidisciplinary clinicians and researchers, and patients to develop or support relevant and evidence-based classification systems of CPP to improve management.

This is the first study to systematically review the systems that have been proposed to classify CPP in men. Many classification systems were identified in the literature, and not all classification systems are appropriate in research and/or to guide clinical practice. The next step is to investigate the evidence either supporting or opposing their use.

Doggweiler, R., Whitmore, K. E., Meijlink, J. M., Drake, M. J., Frawley, H., Nordling, J., Hanno, P., Fraser, M. O., Homma, Y., Garrido, G., Gomes, M. J., Elneil, S., van de Merwe, J. P., Lin, A. T. L., & Tomoe, H. (2017). A standard for terminology in chronic pelvic pain syndromes: A report from the chronic pelvic pain working group of the international continence society. Neurourology and urodynamics, 36(4), 984–1008. https://doi.org/10.1002/nau.23072
Krieger, J. N., Lee, S. W., Jeon, J., Cheah, P. Y., Liong, M. L., & Riley, D. E. (2008). Epidemiology of prostatitis. International journal of antimicrobial agents, 31 Suppl 1(Suppl 1), S85–S90. https://doi.org/10.1016/j.ijantimicag.2007.08.028
Duloy, A. M., Calhoun, E. A., & Clemens, J. Q. (2007). Economic impact of chronic prostatitis. Current urology reports, 8(4), 336–339. https://doi.org/10.1007/s11934-007-0081-x

Continence 7S1 (2023) 100926
DOI: 10.1016/j.cont.2023.100926