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How to diagnose the undiagnosed in a tertiary syncope unit
Dr Frederik J de Lange MD PhD
Amsterdam University Medical Center, The Netherlands
Patients with syncope often remain undiagnosed and untreated. As syncope is a symptom with potentially lethal as well as benign causes, it is important to make a diagnosis. However, due to specialization and subsequent fragmentation in secondary care, physicians often fall back on ruling out causes in their own fi eld. In addition, the most prevalent cause of syncope; reflex syncope, has not been claimed by any specialty. This results in a low diagnostic yield and lots of untreated patients. The yield in emergency departments and secondary care hospital-wide has been studied, and is highly variable. The diagnostic yield of a tertiary syncope unit has yet to be determined. We assessed for the first time the diagnostic yield, accuracy, and safety of a tertiary syncope unit with a dedicated structured approach of three diagnostic phases.
Consecutive syncope patients presenting to our tertiary syncope unit were included. The consultation consisted of phase-1: history taking followed by phase-2: autonomic function testing. After each phase-1 and phase-2 a diagnosis was made and the physician’s subjective probability of the diagnosis was recorded: certain (100%), highly likely (80-100%) and likely (60-80%).
The diagnostic yield was defi ned as the rate of patients that received a certain, highly likely and likely diagnosis after both phase-1 and phase-2. Phase-3 consists of critical follow up by a multidisciplinary expert committee reviewing the Phase-1 and Phase-2 diagnoses by protocol.
This critical follow up was used as a gold standard to assess the diagnostic accuracy and safety. During Phase-3, patients filled in a questionnaire after 3-6 months and after 1-1.5 years, assessing the number of recurrences, changes in treatment, outcomes of testing, and changes in diagnoses.
264 patients were included. Mean age was 51y (IQR: 34-64y), patients experienced six (IQR: 3-20) life-time syncopal episodes and three (IQR: 1-6) episodes last year.
Patients underwent a median of 11 diagnostic tests and consulted a median of 6.5 specialists before the syncope unit consultation. Prior to consultation 134 patients still did not have a suggested diagnosis of the referral physician. After history taking in tertiary SU, 250 out of 264 (94.7%) patients were diagnosed. Autonomic testing yielded six additional diagnosis after Phase-1, did not change the phase-1 diagnosis but increased the subjective probability of the physician (Figure). After phase-3 the overall accuracy of the tertiary diagnoses appeared to be 90.6% compared with diagnostic accuracy of 47% of the referral physician in the secondary care. No cardiac syncope was missed. Three patients were diagnosed with epilepsy after follow-up whom all were seen by neurologist.
A tertiary syncope unit has a high diagnostic yield with a high accuracy, and is safe. Patients underwent many tests prior to the consultation of the tertiary syncope unit resulting in a low yield by the physician in secondary care. History taking is the most important diagnostic tool as additional autonomic testing tailored on history taking, 1) did not change the phase-1 diagnosis after history taking but increased certainty of the diagnosis 2) increased yield in patients with unexplained syncope after history taking. This study emphasizes the need for taking time for thorough history taking in case of highly complex patients with unexplained syncope. Earlier referral to a syncope unit may result in a shorter time to the correct diagnosis with less costs.
Accuracy by an expert committee should be assessed in every study focussing on diagnosing patients with transient loss of consciousness, although this is seldom done currently.