This may lead to inconsistent conclusions and make comparisons between surveys using different instruments difficult, if not invalid.
The small number of RCTs using QoL scales makes identifying trends for QoL instruments difficult.
Another limitation of our review is that, out of 382 RCTs examined, we identified 67 RCTs that used QoL measurements (18%), which makes identifying trends for individual QoL instruments difficult.
The variations in which instruments were used across countries made it difficult to evaluate country-specific results for individual instruments.
Tying can be difficult when using wires.
Eno mastered the instrument by using it as something other than an instrument.
To assess caregiver QOL, different methods and instruments were used; therefore, comparison among studies was difficult.
A range of health-related quality-of-life instruments were used in the studies, which makes comparisons difficult.
Although differentiation between pain and, for instance, anxiety or discomfort is difficult, in the present study specific observational instruments were used.
Comparisons with other follow-up studies are difficult, as various patient inclusion criteria and measuring instruments were used in each case.
