We read with interest the elegant study by Kraus et al. in the August issue of Hepatology. We have some concerns with regard to possible bias due to confounding factors not taken into account in the study. It is well known that not only depression but also the emotional state of the patient and motivation alone can modify neurocognitive function.
It is very common for interferon alpha (IFN-α) therapy to induce depression or dysthymia. The psychiatric adverse effects of IFN-α can last for a long period after ending therapy, whether the patient achieved sustained virological response (SVR) or not. The authors give no data about such an important and proven factor in cognitive test performance.[3, 4] A depressed or dysthymic patient will not perform as well as an euthymic patient in the measured tasks (alertness, attention, vigilance and working memory), no matter how simple. No information is given with regard to the distribution in both groups of this side effect, what medication was used in case it appeared, or if they responded to the antidepressant medication.
Furthermore, the study was not blinded and we assume the patients were informed of the progress of their antiviral therapy. This creates an unavoidable psychological bias. The authors explain that their excellent SVR rate (69% versus the usual 40 to 50%) is explained in part due to the motivation of the studied patients. However, they do not consider that the same factor influences the neuropsychological test they performed. Motivated patients, perhaps those who achieved SVR, perform better on the Test for Attentional Performance (TAP) as compared to unmotivated patients.
Pablo SolÍs-Muñoz, M.D., Ph.D.1,3
Carlos Mingote-Adán, M.D., Ph.D.2
Jose Antonio SolÍs-Herruzo, M.D., Ph.D.3
1Angloamerican Medical Unit Gastroenterology and Hepatology Madrid, Spain
2PAIPSE, Department of Psychiatry University Hospital “12 de Octubre” Madrid, Spain
3Biomedical Research Unit of Gastroenterology and Hepatology University Hospital “12 de Octubre” Madrid, Spain