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There are a number of factors we need to consider regarding all cardiac investigations:
What is “normal”?
- Normal biological variability is based on 95% of a representative population (sample), for example, a Troponin result will have a normal range for men and women and a cut-off point will have been set (by the Laboratory staff) as to when this measurement is considered abnormal.
- Blood test results may or may not be in the normal range. It is important to look at not just the result but also the “trend” for that individual , for example, a patient’s Haemaglobin level may be “low” but in reviewing several blood test results over a long period of time, it has not changed and this is “normal” for that patient.
Machine error
- Be aware that, for example, ECG machine interpretation is usually 85% correct. The other 15% can be completely wrong, so don’t rely on the machine’s automated analysis.
Human error
- Echocardiography, for example, is very dependent on human judgement. The operator marks the points that various measurements are taken from.
Clinical context
- Results must be interpreted in the clinical context, not in isolation. The individual patient’s clinical history must be taken into consideration.
Clinical significance.
- An abnormal test result may not have clinical significance, for example, Right Bundle Branch Block or occasional atrial ectopics on the ECG are not “normal” but the likelihood is that these are not causing the patient any harm.
Introduction
Sensitivity & Specificity…
Page last reviewed: 30 Jul 2020