Thresholds derived from quantification in imaging are increasingly used to define disease. This derivation is not an exact science. When one uses a threshold to define a disease, one does not clearly demarcate disease from normality because the threshold includes overlapping spectra of mild disease and normality. Thus, use of the threshold will mislabel normal individuals with disease. In this perspective, we will describe how the threshold has been derived for left ventricular noncompaction cardiomyopathy, the statistical biases in the design of studies used to derive the threshold, and the dangers of overdiagnosis when the threshold is used to rule out left ventricular noncompaction cardiomyopathy.
Definitions are important to diagnose, prognosticate, and treat a disease. To increase consistency and reduce uncertainty, we increasingly ask for objective criteria to establish disease. For example, chronic bronchitis is defined by a productive cough on most days for at least 3 months for 2 years.
It is neither always desirable nor feasible to obtain tissue for confirmation of disease, particularly cardiac disease, as biopsies have morbidity and sampling error. There is reliance on imaging for diagnosis, and imaging is therefore increasingly used to objectify the positivity of disease. A threshold is the minimum required to fulfill disease status.
Thresholds oversimplify the complexity of diagnosis by assuming a dichotomy between those with a particular disease and those without . In reality, there exists spectrum of disease, as well as spectrum of “nondisease.” The compositions of groups can vary from one study and one clinical situation to another, which affects the generalizability of measurements made on any group. This leads to the establishment of diagnostic thresholds that are inaccurate when used in real-world clinical scenarios.
Left ventricular noncompaction cardiomyopathy (LVNC) is a rare disease, previously under-recognized, characterized by a bilayered myocardium with an abnormally trabeculated subendocardial layer of the myocardium with prominent trabeculae and recesses .
The clinical and phenotypic presentations are variable, and it is recognized that patients with a severe phenotype have a poor prognosis from progressive heart failure, embolic phenomena, and malignant arrhythmias.
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Establishment of a threshold
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Application of thresholds to wider populations
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Biases in studies of diagnostic test accuracy
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Optimizing the use of imaging in the diagnosis of LVNC
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References
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