The minimal clinically important difference determined using item response theory models: an attempt to solve the issue of the association with baseline score.
OBJECTIVE
Determining the minimal clinically important difference (MCID) of questionnaires on an interval scale, the trait level (TL) scale, using item response theory (IRT) models could overcome its association with baseline severity. The aim of this study was to compare the sensitivity (Se), specificity (Sp), and predictive values (PVs) of the MCID determined on the score scale (MCID-Sc) or the TL scale (MCID-TL).


METHODS
The MCID-Sc and MCID-TL of the MOS-SF36 general health subscale were determined for deterioration and improvement on a cohort of 1,170 patients using an anchor-based method and a partial credit model. The Se, Sp, and PV were calculated using the global rating of change (the anchor) as the gold standard test.


RESULTS
The MCID-Sc magnitude was smaller for improvement (1.58 points) than for deterioration (-7.91 points). The Se, Sp, and PV were similar for MCID-Sc and MCID-TL in both cases. However, if the MCID was defined on the score scale as a function of a range of baseline scores, its Se, Sp, and PV were consistently higher.


CONCLUSIONS
This study reinforces the recommendations concerning the use of an MCID-Sc defined as a function of a range of baseline scores.
U669 -Mental Health and Public Health, Inserm, Maison de Solenn, 97 boulevard du Port-Royal, 75014 Paris, France; UMR-S0669, Université Paris-Sud and Université Paris Descartes, Maison de Solenn, 97 boulevard du Port-Royal, 75014 Paris, France; Research Unit on Children's Psychosocial Maladjustment, University of Montreal, 3050 Édouard Montpetit, H3T 1J7, Montreal, Quebec, Canada; EA 4275, Biostatistics, Clinical Research and Subjective Measures in Health Sciences, University of Nantes, Faculté de Médecine & Pharmacie, 1, rue Gaston Veil - BP 53508, 44035 Nantes Cedex 1, France; Department of Public Health, University of Angers, CHU Angers- 49933 Angers cedex 9, France. Electronic address: alex.rouquette@gmail.com.
Alexandra
A
Rouquette
EA 4275, Biostatistics, Clinical Research and Subjective Measures in Health Sciences, University of Nantes, Faculté de Médecine & Pharmacie, 1, rue Gaston Veil - BP 53508, 44035 Nantes Cedex 1, France.
Myriam
M
Blanchin
EA 4275, Biostatistics, Clinical Research and Subjective Measures in Health Sciences, University of Nantes, Faculté de Médecine & Pharmacie, 1, rue Gaston Veil - BP 53508, 44035 Nantes Cedex 1, France.
Véronique
V
Sébille
EA 4360 APEMAC, INSERM CIC-EC CIE6 and CHU Nancy, Université de Lorraine and Université Paris Descartes, 9 avenue de la Forêt de Haye, BP 184, 54505 Vandoeuvre les Nancy cedex, France.
Francis
F
Guillemin
Research Unit on Children's Psychosocial Maladjustment, University of Montreal, 3050 Édouard Montpetit, H3T 1J7, Montreal, Quebec, Canada; Department of Preventive and Social Medicine, University of Montreal, C.P. 6128, succursale Centre-ville, Montréal (Québec) H3C 3J7.
Sylvana M
SM
Côté
U669 -Mental Health and Public Health, Inserm, Maison de Solenn, 97 boulevard du Port-Royal, 75014 Paris, France; UMR-S0669, Université Paris-Sud and Université Paris Descartes, Maison de Solenn, 97 boulevard du Port-Royal, 75014 Paris, France; Department of Public Health, Paul Brousse Hospital, 12, avenue Paul-Vaillant-Couturier, 94804 Villejuif cedex, France.
Bruno
B
Falissard
EA 4275, Biostatistics, Clinical Research and Subjective Measures in Health Sciences, University of Nantes, Faculté de Médecine & Pharmacie, 1, rue Gaston Veil - BP 53508, 44035 Nantes Cedex 1, France.
Jean-Benoit
JB
Hardouin
D000368:Aged; D006801:Humans; D008962:Models, Theoretical; D017063:Outcome Assessment, Health Care; D057566:Self Report; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*
Item response theory; Minimal clinically important difference; Patient-reported outcomes; Questionnaires; Rasch models; Sensitivity and specificity