Page 87 - The value of total hip and knee arthroplasties for patients

Distinctiveness of Psychological Constructs
but do have considerable theoretical differences, though we did not expect such a strong correlation.We therefore also performed a post-hoc analysis to investigate the influence of the strong correlation between hope and optimism on model fit. Results showed that the five factor model had a significantly better fit than the four factor model in which optimism and hope were forced to load on one factor.
In a third post-hoc analysis we investigated the possibility that a model in which,
besides the five separate factors, a general factor is included that accounts for
shared variance in all items would fit the data. Results showed that this model fit
the data better than any other model tested and that there is a strong general
factor that accounts for a large amount of the variance of the total bifactor model.
Thus, we suggest that there is a general ’outlook on future’ factor that underlies
each of the items. Separately, there are four more specific factors namely treatment 5 credibility, treatment expectancy, optimism and pessimism that each account for
unique variance above this general factor. Hope however did not account for a substantial amount unique variance above the general factor.
Our findings are consistent with previous factor analyses that have shown hope and optimism to be related but distinct constructs.2;25 Our study has extended these findings by demonstrating this in patients undergoing THA and TKA as well as by additionally considering treatment specific future oriented psychological constructs. Our results however slightly differ from Magaletta and Olivers25 study because we found that the five factor model which included pessimism as a separate factor showed better model fit compared a four factor model in which all items of the LOT-R loaded on one factor.This could be a result of the use of the Dutch translation of the LOT-R which has shown to have a two-dimensional structure 43 Similar to previous studies we found that optimism and hope are positively related and that both of these are negatively related to pessimism.2;5
Studying the conceptual overlap of psychological constructs seems to gain more importance. A reason for this is that many psychological measures have been developed in the last decades and all of them have individually shown to measure important constructs in medical care but considerable overlap may exist between these constructs (and measures), causing lack of conceptual clarity and confusion among researchers and care providers about which psychological measures to use in studies and daily practice. Therefore, studies investigating conceptual overlap or distinctiveness of these constructs within a medical care setting are important.
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