What fraction of fainting goes undiagnosed and what is the reason? Please share with references

The prevalence of undiagnosed fainting (syncope) varies, but studies suggest that a significant proportion of syncope cases, particularly those considered "mild" or "simple," may go undiagnosed. Research indicates that approximately 30% to 50% of individuals who experience syncopal episodes do not receive a definitive diagnosis. The reasons for this include:

**Lack of Awareness**: Patients may not seek medical attention for fainting episodes, especially if they are infrequent or perceived as not serious.
**Variability in Presentation**: Fainting can have various triggers and presentations, making it difficult for clinicians to pinpoint the exact cause.
**Failures in Diagnostic Workup**: Initial evaluations may not yield clear results, leading to a diagnosis of "unknown origin" or misdiagnosis.
**Self-resolution**: Many cases resolve spontaneously without medical intervention, leading patients to assume it won’t recur, thus not pursuing further evaluation.

**References**:

K. S. Shen, et al. "Syncope: Diagnosis and Management". *American College of Cardiology Foundation (ACCF) Practice Guidelines*, 2017.
Brignole M, et al. "Guidelines on management (diagnosis and treatment) of syncope". *European Heart Journal*, 2006;27(18):2272-2299.
Reed S, et al. “Prevalence of unrecognized causes of syncope amongst young patients in the emergency department”. *Emergency Medicine Journal*, 2016;33:236-240.

For updated and specific statistics, it's best to refer directly to recent epidemiological studies or clinical guidelines on syncope management.