timetodiagnosis

Time to diagnosis refers to the period between the onset of a patient’s symptoms and the establishment of a formal diagnosis by a clinician. It is used as a quality-of-care metric and an indicator of diagnostic timeliness in healthcare systems and research. Depending on the study, time to diagnosis may be defined in different ways, such as onset-to-diagnosis, first healthcare contact-to-diagnosis, or the overall diagnostic interval that combines patient and system delays.

The construct encompasses several phases. The patient interval covers delays before seeking care after symptom onset. The provider interval includes times from initial assessment to diagnostic confirmation, including referrals, testing, and second opinions. The diagnostic interval is the total duration from symptom onset to diagnosis. In some contexts, the term diagnostic delay is used more broadly to describe delays within any part of this process.

Why timeliness matters varies by condition. For many diseases, earlier diagnosis can improve prognosis, reduce disease progression, and optimize treatment outcomes. However, measuring time to diagnosis must be interpreted cautiously, as earlier labeling does not always translate into better outcomes due to factors such as lead-time bias or overdiagnosis.

Factors affecting time to diagnosis include patient-related aspects (symptom recognition, health literacy, access to care, socio-economic barriers), system-related elements (availability of primary and specialty care, diagnostic testing capacity, referral networks), and disease characteristics (nonspecific or evolving symptoms, rarity, and variability in presentation).

Measurement challenges include reliance on patient recall for onset, variability in defining the start of care, and incomplete documentation. Despite these challenges, time to diagnosis is used to benchmark performance, evaluate interventions, and study diagnostic processes across settings. Related concepts include patient interval, system interval, diagnostic delay, and time to treatment.