Life expectancy for pediatric liver transplant patients has significantly improved over the last decade, with patient perceived health-related quality of life (HRQOL) assuming greater importance in determining the quality of the enhanced survival of these pediatric patients [1
]. In the largest multicenter study published to date, involving 873 pediatric liver transplant patients ages 2 to 18 years surviving liver transplantation at least 12 months, pediatric liver transplant patients evidenced significantly lower generic HRQOL compared to a matched healthy sample, with the largest differences demonstrated in school functioning [2
Chronic liver disease and the liver transplantation process may specifically impact cognitive functioning in pediatric recipients since the child is exposed to numerous risk factors during a crucial stage of brain development including hepatic encephalopathy, malnutrition resulting from chronic liver disease, exposure to neurotoxic medications, and portal systemic shunting [3
]. Previous studies with pediatric liver transplant recipients, using lengthy and complex standardized cognitive and intelligence testing batteries, have demonstrated that pediatric patients with liver transplants are at increased risk for cognitive impairments following liver transplantation [3
]. A recent multicenter study, for example, examined the prevalence of cognitive and academic delays in children following liver transplant [7
]. One hundred and forty-four patients 2 years post-liver transplant performed significantly below test norms on standardized intelligence quotient (IQ) and achievement measures. Twenty-six percent of patients had mild to moderate IQ delays and 4% had serious delays. Reading and/or math scores were weaker than IQ in 25%, suggesting learning disability. These results, along with others, demonstrate a higher prevalence of cognitive and academic delays, and learning problems in pediatric liver transplant recipients compared to the normal population.
Taken together, these findings suggest the importance of routine serial measurement of cognitive functioning in pediatric liver transplant recipients. However, standardized cognitive functioning batteries require the time, expense and the expertise of licensed psychologists, which may serve as a significant barrier to the routine measurement of cognitive functioning in this at risk population during regularly scheduled medical office and clinic visits, as well as for multisite national and international clinical trials. This prior literature underscores the need for a brief, reliable and valid cognitive functioning measure that can be completed by pediatric patients and their parents.
The 6-item PedsQL™ Cognitive Functioning Scale was designed as a brief and easy to administer patient self-reported and parent proxy-reported generic symptom-specific instrument to measure cognitive functioning across pediatric populations, originally developed in a pediatric cancer population [8
]. Subsequently, the PedsQL™ Cognitive Functioning Scale has been demonstrated to be significantly associated with the 72-item Behavior Rating Inventory of Executive Function (BRIEF), a widely validated measure of executive functioning, in a pediatric head trauma sample [9
]. Executive functioning encompasses a constellation of higher-order neurocognitive processes reflective of sustained attention, selective attention, working memory, planning, organizing, inhibition, initiation, response selection, reasoning, and problem-solving [10
]. In the pediatric head trauma sample, the PedsQL™ Cognitive Functioning Scale correlated highly not only with individual subscales of the BRIEF, but also with the BRIEF summary scores (r
s = -.67, -.70, and -.55 for the Global Executive Composite, Metacognition Index, and Behavioral Regulation Index, respectively) [9
], suggesting that the PedsQL™ Cognitive Functioning Scale may be measuring important aspects of executive functioning.
Although originally imbedded in the PedsQL™ Multidimensional Fatigue Scale [8
], with demonstrated reliability and validity across multiple pediatric chronic health conditions [8
], the PedsQL™ Cognitive Functioning Scale has emerged more recently as a separate symptom-specific instrument in pediatric populations with known or suspected impairments in cognitive functioning [9
]. However, the feasibility, reliability, and validity of the PedsQL™ Cognitive Functioning Scale have not been previously reported in the pediatric liver transplant population.
Consequently, the objective of the present study was to examine the feasibility, reliability, discriminant, construct, and concurrent validity of the PedsQL™ Cognitive Functioning Scale in pediatric patients with liver transplants. We hypothesized that the PedsQL™ Cognitive Functioning Scale would distinguish between pediatric patients with liver transplants and healthy children based on previous findings with other pediatric chronic health conditions, supporting discriminant validity [8
]. We further expected that more impaired cognitive functioning as measured by the PedsQL™ Cognitive Functioning Scale would be significantly correlated with more impaired generic HRQOL as measured by the PedsQL™ 4.0 Generic Core Scales, with medium to larger effect sizes, based on the conceptualization of symptoms as causal indicators of generic HRQOL, supporting construct validity [22
]. We also expected the PedsQL™ Cognitive Functioning Scale to be significantly correlated with parent and teacher reported patient executive functioning as measured by the BRIEF in a subsample of pediatric patients, supporting concurrent validity [9
]. Finally, we explored comparisons between the PedsQL™ Cognitive Functioning Scale in pediatric patients with liver transplants with long-term pediatric cancer survivors to determine the relative impact of cognitive functioning in comparison to a pediatric chronic health condition known to manifest significant cognitive impairments subsequent to chemotherapy and cranial radiation [23