Confirmatory factor analysis of the Patient Assessment of Constipation-Symptoms (PAC-SYM) among patients with chronic constipation

Sebastiano Bonventre, Michela Di Fonzo, Lucia D'Alba, Mario Grassini, Paolo Usai Satta, Gabriele Bazzocchi, Lisa Girardi, Francesca Rogai, Santo Monastra, Leonardo Tammaro, Luca Neri, Leonilde Bonfrate, Alberto Paviotti, Francesca Galeazzi, Donato Francesco Altomare, Vittorio D'Onofrio, Giulia Comandini, Giuseppe Biscaglia, Francesco De Giorgi, Ivano BivianoSilvia Orselli, Andrea Geccherle, Antonio Gasbarrini, Matteo Neri, Sergio Crotta, Luigi Benini, Kostantinos Efthymakis, Mario Del Piano, Maria Marino, Nunzio Ranaldo, Claudio Valle, Maria Cristina Neri, Massimiliano Lo Cascio, Virgilio Clara, Manuela Fortuna, Alberto Paviotti, Vito Annese, Massimiliano Lo Cascio, Piero Portincasa, Roberto Lolli, Renato Bocchini, Giovanni Guarnieri, Nunzio Ranaldo, Donato Francesco Altomare, Renato Cannizzaro, Massimo Bellini, Massimo Bellini, Roberto Antonio Noris, Marzia Groppo, Francesco Torresan, Danilo Badiali, Sebastiano Bonventre, Francesco Giangregorio, Paola Iovino, Rosanna Cogliandro, Emanuele Bendia, Renato Sablich, Renato Cannizzaro, Giampiero Macarri, Giovanni Brandimarte, Sergio Crotta, Michele Cicala, Paolo Ravelli, Rosario Cuomo, Livio Cipolletta, Edda Battaglia, Eleonora Gaetani, Sandro Passaretti, Guido Basilisco, Giancarlo Spinzi, Paolo Pazzi, Michele Di Stefano, Stefania Miraglia, Pierluigi Fiore, Francesco Luzza, Enrico Corazziari, Vincenzo Stanghellini, Alberto Pilotto, Walter Fries, Gabrio Bassotti, Piero Portincasa, Vincenzo Savarino, Francesco Di Mario, Luigi Benini, Massimo Bellini, Donato Francesco Altomare, Paul Maurice Conway, Fabrizio Bossa

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20 Citations (Scopus)


Background and aim: PAC-SYM is widely adopted to asses constipation severity. However, it has been validated in a small sample, few items have been included based on expert opinion and not on empirical grounds, and its factor structure has never been replicated. We aimed at evaluating the psychometric properties of PAC-SYM in patients with chronic constipation. Methods: We enrolled 2,203 outpatients with chronic constipation in two waves. We used wave I sample to test the psychometric properties of the PAC-SYM and wave II sample to cross-validate its factor structure, to assess criterion validity, responsiveness to clinical change, and its minimal clinically important difference. Results: Only a minority of patients reported any rectal tearing (38 %). Deletion of such item leads to a 11-item version (M:PAC-SYM). The remaining items in the rectal domain were moderately correlated with the stool domain. Exploratory factor analysis and confirmatory factor analysis revealed a bifactor structure with two subscales (stool and abdominal symptoms) and a general severity factor. The M:PAC-SYM demonstrated excellent reliability, moderate correlation with SF-12 and treatment satisfaction (r = 0.28-0.45), discrimination across Rome III criteria for functional constipation and abdominal pain, and responsiveness to clinical change (β = -0.49; ω2 = 0.25). M:PAC-SYM minimal clinically important difference was 0.24. Conclusion: Our analysis shows that the rectal domain may not represent a relevant cluster of symptoms for patients with chronic constipation. We developed a modified version of the PAC-SYM which might better represent symptom severity of most patients seeking care in gastroenterology referral centers.
Original languageEnglish
Pages (from-to)1597-1605
Number of pages9
JournalQuality of Life Research
Publication statusPublished - 2015

All Science Journal Classification (ASJC) codes

  • Public Health, Environmental and Occupational Health


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