Diagnosegrenzen

Diagnosegrenzen, or diagnostic thresholds, describe the boundary values or criteria used to classify a patient as having a disease, or as not having it, based on diagnostic tests, signs, symptoms, or established criteria. They translate quantitative measurements into binary decisions, such as disease present or absent. In practice, diagnosegrenzen are determined through statistical analysis, clinical judgment, and guideline consensus. Common methods include ROC curve analysis to select a cutoff that optimizes sensitivity and specificity, often using the Youden index; consideration of the trade-offs between false positives and false negatives; and context-specific factors such as disease prevalence and consequences of misclassification.

Examples include HbA1c thresholds for diabetes (often ≥6.5%), fasting glucose ≥126 mg/dL, and blood pressure thresholds for hypertension (e.g., 130-139 systolic or 80-89 diastolic depending on guidelines); imaging criteria like radiographic grading thresholds; and diagnostic criteria in psychiatry such as DSM-5 symptom counts and duration.

Limitations include that thresholds are population- and method-dependent; they can vary between laboratories and guidelines; they may change with new evidence; and they can contribute to overdiagnosis or underdiagnosis when misapplied.

Diagnosegrenzen function as practical tools to support clinical decision-making, screening, and epidemiological interpretation, but they do not replace comprehensive clinical assessment and individualized consideration of risks and benefits.