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Wednesday, 13.12.2017

Per Bech: Clinical Psychometrics

Aitor Castillo’s comment

 

From the outset, this 213-page book captures the interest of the reader. The edition is clean, precise, clear and orderly. As soon as I opened it, I said to myself:  “This is a book I have to read.”

At the very beginning, being a clinical psychopharmacologist, I felt frightened of not being capable of understanding these psychometrics’ issues. However, the author reassures us: “(the psychometric procedures) are presented for readers without any requirement of particular mathematical-statistic knowledge” or, in other words, “these models have been amended for readers without mathematical knowledge.”

By the way, I wonder how Per Bech was able to say so much in just one and a half pages in the introduction section. And I would add that I enhanced my neuroplasticity reading about so many bright people who contributed to the development of such an important area like Clinical Psychometrics.

I think that in order to take full advantage of this book, the reader needs to be familiar with the concepts and practice of psychopharmacological clinical trials and, of course, to have the necessary insight about the phenomenological and clinical aspects of mental illness.

I want to concentrate, in a very specific way, on chapter five, “The Clinical Consequence of IRT Analyses: the Pharmacopsychometric Triangle,” because it appears as very useful and evidence-forming to me. The data derived from the review of significant clinical drug trials are of great value to the clinician.

Through this review, we learn that an effect size higher than 0.40 was only achieved on 10 mg donepezil using the Mini Mental State Examination. If the Alzheimer’s Disease Assessment Scale was used, both 5 mg and 10 mg donepezil achieved an effect size of 0.47 and 0.58, respectively.

Regarding antipsychotic medications, haloperidol doses of 4, 8 and 16 mg are effective with an effect size of 0.50, 0.73 and 0.55, respectively. At the same time, it is reassuring that even such a relatively low dose as 4 mg of haloperidol causes considerable Parkinsonian symptoms, and the highest dose of 16 mg causes very severe side effects without any signs of remission of depressive symptoms and consequently no increase in quality of life.

Of the utmost importance are the numerous references to historical issues regarding the development and studies of some psychopharmacological drugs and their applications to the treatment of mental disorders. For example, the study performed at the Psychiatric Department of the Danish Rigshospitalet showed that severely manic patients could respond after six days of treatment with a fixed dose of 10 mg haloperidol and that the patients with the highest plasma concentration showed the best response. In another study at the University Hospital of Geneva, manic women responded after 14 days on an olanzapine dose of 20 mg and, again, the patients with the highest plasma concentration had the most pronounced effect.

The author wisely says that it is vital to use the HAM-D6 in dose-response relationship studies, taking into account that many side effects are listed as depressive symptoms in the HAM-D or MADRS.

Thus, regarding antidepressive medications, it is quite interesting to know that 10 mg escitalopram was an inadequate dose in patients with a marked degree of depression (≥30 at baseline on the MADRS), while both 40 mg of citalopram and 20 mg escitalopram achieved an effect size greater than 0.40.

A landmark study including the WHO-5 quality of life scale noted that 50 mg desvenlafaxine led to FDA approval. However, the effect size only reaches 0.40 on the HAM-D6 for this dose.  Interestingly enough, the 100 mg desvenlafaxine reached an effect size above 0.40 on the HAM-D17, HAM-D6 and the WHO-5.

Given the fact that anxiety disorders are among the most prevalent mental disorders, it is necessary to have some insight into the anxiolytic drugs. Fortunately, the author emphasized that 150 mg pregabalin is an inadequate dose, with a HAM-A14 effect size of 0.31, and only 0.20 on the valid HAM-A6. Pregabalin doses between 200 mg and 450 mg gave a HAM-A14 effect size of 0.56 and a HAM-A6 effect size of 0.49. Higher doses did not result in larger effect sizes. On the other hand, the alprazolam effect size is about 0.35 on the HAM-A14 and HAM-A6. Along the same lines, 75 mg venlafaxine showed an effect size of 0.40 on the HAM-A6 and 0.31 on the HAM-A14.

Finally, a dose of lithium resulting in plasma concentrations between 0.8 and 1.2 mmol/l is most effective for an acute antimanic effect. For antidepressant augmentation, a concentration between 0.3 and 0.5 mmol/l is most effective.

However, for long-term mood stabilization a concentration between 0.5 and 0.8 mmol/l is most appropriate. In this concentration range, lithium has no sedative effect on the functions relevant to car driving.

Coming back to a more general perspective, the book also provides a very informative glossary section and an extremely useful appendix including many psychometric scales.

My conclusion is that Bech’s book is a must read for clinicians who want to attain a comprehensive knowledge of psychopharmacological research and are looking forward to work in this fascinating area of Psychiatry. In this context, clinical psychometrics does an incommensurable service.

 

 

Aitor Castillo

December 22, 2016