Number Needed To Treat

An alternative way to allow for the variation in treatment effect upon QoL is known as the number needed to treat (AWT). This is an estimate of the number of patients who need to be treated with the new treatment in order for one additional patient to benefit. The NNT can be estimated whenever a clinical trial has a binary outcome. When evaluating QoL, one possible binary outcome might be the proportion of patients with a moderate improvement in QoL, where moderate improvement could be defined...

Discriminative Evaluative And Predictive Instruments

Throughout the stages of scale development, validation and evaluation it is important to consider the intended use of the measurement scale. Guyatt, Feeny and Patrick (1993) draw attention to the need to distinguish between discriminative, evaluative and predictive instruments. Some scales are intended to differentiate between people who have a better QoL and those with a worse QoL these are discriminative scales. Other scales are intended to measure how much QoL changes these are evaluative...

Prognostic Factors

In many clinical situations the appropriate treatments and the patients' final choice of therapeutic option may differ depending on circumstances. Nevertheless there may be groups of patients, perhaps pre-menopausal women with breast cancer, who might choose a different approach from that chosen by post-menopausal women with the same disease. The Q-TWiST methodology extends to this situation and can also be used for comparing patient groups receiving the same treatment. From such studies one...

Multidimensional Fatigue Inventory MFI

The MFI of Smets et al. (1995) is a 20-item self-report instrument designed to measure fatigue (Appendix E14). It covers five dimensions, each of four items general fatigue, physical fatigue, mental fatigue, reduced motivation, and reduced activity. There are equal numbers of positively and negatively worded statements, to counter possible response bias, and the respondent must indicate to what extent the particular statement applies to him or her. The five-point items take responses between...

Paediatric Asthma Quality of Life Questionnaire PAQLQ

The PAQLQ developed by Juniper et al. (1996) has been designed to measure the problems that children between the ages of 7 and 17 experience as a result of asthma extracts from the self-administered version are shown in Appendix El 1. The PAQLQ has 23 items relating to three dimensions, namely symptoms, activity limitations and emotional function. Items are scored from 1 to 7. Three of the activity questions are individualised with the children identifying important activities at the beginning...

Quality of Life in Epilepsy QOLIE89

In contrast with the previous examples, the QOLIE-89 is a 13-page, 89-item questionnaire aimed at patients with epilepsy (Devinsky et al., 1995) Appendix E10 shows extracts. It is based upon a number of other instruments, in particular the SF-36, with additional items from other sources. It contains five questions concerning worry about seizures, and questions about specific bothersome epilepsy-related limitations such as driving restrictions. Shorter versions with 31 and 10 items are...

Interrater Reliability

Inter-rater reliability concerns the agreement between two raters. However, for QoL purposes we are principally interested in the patient's self-assessment. Many studies have shown that observers such as healthcare staff and patients' relatives make very different assessments from the patients themselves. Therefore, for validation of a QoL instrument, inter-rater reliability is usually of lesser concern than test-retest reliability. Since the patients are usually regarded as the best assessor...

Barthel Index of Disability BI

Disability scales were among the earliest attempts to evaluate issues that may be regarded as related to QoL. They are still commonly employed, but mainly as a simple indication of one aspect of the patient's overall QoL. The BI (Mahoney and Barthel, 1965) was developed to measure disability, and is one of the most commonly used of the class of scales known as activities-of-daily-living (ADL) scales. ADL scales focus upon a range of mobility, domestic and self-care tasks, and ignore issues such...

Factor Analysis Of The Hads Questionnaire

We explain how factor analysis works by using an illustrative example. The correlation matrix presented in Table 5.1 showed the interrelationships of the HADS items. Although pre-treatment data were used for this example, we would expect to find very similar results if during- or post-treatment assessments were considered. A standard statistical program, ST AT A 1999 , is used to see how well the hypothesised factor structure is recovered. Very similar output would be obtained from most other...