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Three Part Question

In [adult patients presenting with syncope], [how effective is tilt table testing] in [diagnosing psychogenic blackout]?

Search Strategy

Medline (1948 to June Week 4 2011) and Embase (1980 to week 26 2011) using the Ovid interface.
{[(syncope.mp.) OR (exp Syncope, Vasovagal/) OR (exp Syncope/)] AND [(tilt table.mp.) OR (exp Tilt-Table Test/)] AND [(psychogenic.mp.)]} LIMIT to humans AND english language.

Search Outcome

In Medline 12 papers were found of which four were relevant. Two of these were then of insufficient quality. In Embase 9 papers were found, all of which were irrelevant, other than one duplicate.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Zaidi, A., et al 1999 UK	21 patients were enrolled with previous clinical diagnoses of psychogenic blackout. HUTT was carried out to evaluate its ability to diagnose psychogenic blackout.	Prospective cohort study	Sensitivity of HUTT in detecting psychogenic blackout	81%	Very limited study. No randomisation of patients to include selection of those without the disease (making it impossible to calculative specificity). No reference to statistical power. No ethical approval. No results table to provide ease of reader analysis. Limited reference to patient demographics and the effect of these.
Grubb, B., et al 1992 United States	52 patients took part in the study, 42 with a history of recurrent syncope-like episodes and 10 with a history of seizure-like episodes. Inclusion criteria were 2 episodes in the last six months, without a clear diagnosis. All patients underwent HUTT, and those with a suspected diagnosis of psychogenic blackout were referred to a psychiatrist for confirmation.	Prospective cohort study	Sensitivity of HUTT in detecting psychogenic blackout	100% (see weaknesses however)	Patients with a negative result for psychogenic blackout were not referred to psychiatrists as well - possible source of underdiagnosis. No reference to statistical power. No reference to ethical approval. Paediatric patients were included.
			Specificity of HUTT in detecting psychogenic blackout	100%

Comment(s)

The two studies presented here are of quite a low quality, but together they do have the benefit of demonstrating similar results. The sample sizes were small and there is a lack of randomisation to either include patients without psychogenic blackout or treat them in the same manner as those with. That said, as much as further investigation would be welcomed, there appears to be the outcome that it is possible to diagnose the condition before referral to psychiatry. While that doesn't prevent a referral occurring - it is obviously necessary in order to instigate treatment, it does ensure that the process begins as soon as possible without starting the patient on other treatments beforehand, i.e. anticonvulsants.

Clinical Bottom Line

It is possible to diagnose psychogenic blackout using a tilt table test.

References

1. Zaidi, A., Crampton, S., Clough, P., Fitzpatrick, A., et al. Head-up tilting is a useful provocative test for psychogenic non-epileptic seizures. Seizure 1999; 353-355
2. Grubb, B., Gerard, G., Wolfe, D., et al. Syncope and Seizures of Psychogenic Origin: Identification with Head-Upright Tilt Table Testing. Clin Cardiol 1992; 839-842