Patient reports of health outcome for adults living with sickle cell disease: development and testing of the ASCQ-Me item banks

Table 6 Reliability and validity of ASCQ-Me item banks

Question sets	Score range at < 0.33 SE^§	Internal consistency reliability	Model fit^ψ		Corr. between models*	Relat. to SCD severity (F-stat**)
Question sets	Score range at < 0.33 SE^§	Internal consistency reliability	CFI^¥	RMSEA^ǂ	Corr. between models*	Relat. to SCD severity (F-stat**)
Cognitive Impact	3.7	0.95	0.95	0.10	0.96	02.92
Emotional Impact	4.1	0.96	0.93	0.09	0.97	16.56
Pain	4.0	0.95	0.94	0.09	0.96	31.67
Sleep Impact	4.1	0.92	0.98	0.08	0.96	12.13
Social Impact	4.8	0.95	0.95	0.10	0.96	20.51
Stiffness	4.4	0.95	0.94	0.11	0.96	38.72

^§This is out of a total scale score range of 6 which includes those at the very top and bottom of the range.
^ψConfirmatory Factor Analysis was conducted using structural equation modeling in which the responses to each question were modeled as comprised of the influence of a single dimension and a number of group factors.
^¥Comparative fit index (CFI) compares the variance explained by the model to the total amount of variance in the data. The CFA runs from “0” (no relationship between the predicted and observed correlation matrix) to “1.0” (the predicted correlation matrix is identical to the observed).
^ǂRoot Mean Square Error of Approximation (RMSEA) is the amount of variance that is not predicted by the model.
*These are the correlations between the vector of discrimination parameters for the bi-factor with the uni-factor Item Response Theory Graded Response Model (IRT GRM) which indicate the amount of agreement between the two models in the relationship of items to the underlying construct.
**All F-statistics were significant at p < 0.0001 with the exception of that associated with the cognitive functioning measure which was > 0.05.

ISSN: 1477-7525