Diagnostic reliability of clinical laboratory parameters – criteria. Requirements to the criteria of diagnostic reliability of clinical laboratory tests in different group of diseases.
Criteria:
- Diagnostical sensitivity: Determined by dividing the true positives by the sum of the true positives and false negatives
- Diagnostical Specificity: the ability of a test to detect a true negative; determined by dividing the true negatives by the sum of the true negatives and false positives.
- Positive predictive value: The predictive value of a positive test result is the fraction of positive test results which are correct, or the true positives divided by all the positives, both true and false
- Negative predictive value: The predictive value of a negative test is the fraction of all negative results which are correct, or the true negatives divided by all the negatives, both true and false
Requirements to the criteria of diagnostic reliability of clinical laboratory tests in different group of diseases
- Diagnostical reliability expressed by the diagnostical sensitivity, specificity, predictive value and effectiveness, depends of the value of the selected reference limit, that is by cut off value.
- Critical for the selection of the limits of the reference range is to find such a relationship in which the sensitivity and specificity of a particular clinical laboratory test have optimum value
- 3.Knowledge of diagnostical sensitivity and specificity required to discuss the reference range is not the laboratory test at all, and for the particular condition
High diagnostical sensitivity (close to 100 %)is required in serious, but curable diseases.
High diagnostical specificity is required in severe, incurable diseases (such as some forms of malignant tumours).
Diagnostical effectiveness is the possibility( in %) of a test to direct correctly at a diagnosis both when there is or isn’t concrete disease.
High diagnostical effectiveness (high sensitivity and high specificity of a laboratory test is desirable in severe diseases with a possibility of successful treatment