Dictionary of Evidence-based Medicine.pdf
Dictionary of Evidence-based Medicine.pdf
Dictionary of Evidence-based Medicine.pdf
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70 <strong>Dictionary</strong> <strong>of</strong> <strong>Evidence</strong>-<strong>based</strong> <strong>Medicine</strong><br />
Global measures<br />
In the assessment <strong>of</strong> perception, a global measure is one where the person<br />
makes a single assessment about the overall value <strong>of</strong> an intervention on his<br />
or her own status. Two types <strong>of</strong> global measures are <strong>of</strong>ten used in healthrelated<br />
quality <strong>of</strong> life assessments: (i) preference measures by which the<br />
subjects express a judgement about how much they would be prepared to<br />
sacrifice in order to achieve perfect health; (ii) rating scales by which<br />
patients rate their health status using categorical descriptive labels or<br />
analogue (continuous) scales. All rating scales are usually anchored so that<br />
the two ends <strong>of</strong> the scales refer to perfect health and as good as dead. States<br />
<strong>of</strong> health worse than death may be assigned negative values, particularly<br />
in community-derived scales.<br />
In preference measurements, what is being traded for perfect health can<br />
be years <strong>of</strong> life, risk <strong>of</strong> death or money. The method is then referred to as<br />
time trade-<strong>of</strong>f, standard gamble or willingness to pay respectively. Global<br />
values using both preference measures and rating scales can be transformed<br />
to a utility scale ranging from 0 to 1. These utilities can then be<br />
used for quality-adjusting life-years to yield QALYs, a basic unit in cost<br />
utility analyses.<br />
Gold standard<br />
The term 'gold standard' in measurement scale development or pharmacoeconomic<br />
evaluation refers to the comparator which is generally regarded<br />
to be the best available. For example, in the survey <strong>of</strong> health status, the<br />
SF-36 form is <strong>of</strong>ten regarded as the gold standard. Therefore when<br />
developing or proposing a new form, it is expected that any validation<br />
would include the concurrent use <strong>of</strong> SF-36.<br />
Good clinical practice<br />
Good clinical practice for the conduct <strong>of</strong> a clinical trial defines what needs<br />
to be done before, during and after completion <strong>of</strong> the trial to ensure full<br />
accountability. The steps required for GCP are defined in a guideline issued<br />
by the International Conference on Harmonization (ICH) <strong>of</strong> technical<br />
requirements for registration <strong>of</strong> pharmaceuticals for human use. While the<br />
health ministries <strong>of</strong> different countries will have their own criteria, the<br />
ICH guideline summarizes the consensus views <strong>of</strong> regulatory authorities<br />
in the USA, the European Community and Japan after wide-ranging<br />
consultation with interested parties such as the pharmaceutical industry.<br />
Issues such as informed consent, ethics committee approval, randomization<br />
list, subject enrolment log and reporting <strong>of</strong> adverse drug reactions are