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Three Part Question

In [adult patients presenting with syncope], [how effective is lying and standing blood pressure] in [diagnosing orthostatic hypotension]?

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 [((lying and standing).mp.) OR (blood pressure measurement.mp.) OR (exp Blood Pressure Determination/)] AND [(orthostatic hypotension.mp.) OR (postural hypotension.mp.) OR (exp Hypotension, Orthostatic/)]} LIMIT to humans AND english langauge.

Search Outcome

In Medline 8 papers were found of which only one was relevant. In Embase 26 papers were found, one was new and relevant and one was a duplicate of the Medline paper.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Cooke, J., et al 2009 Ireland	1452 consecutive patients who underwent head-up tilt testing between 1998 and 2008. All were referred for investigation of orthostatic hypotension or recurrent falls. 722 patients were excluded either due to being unable to stand safely, or time restraints, but there were no significant differences in the age or sex of the two groups. The result of the sitting and standing BP was compared to a "gold standard" of HUTT to diagnose orthostatic hypotension.	Retrospective cohort study	Sensitivity	15.5%	No reference to statistical power. No blinding of investigators. Sitting and standing BP is not exactly the same as lying and standing BP, as asked in the clinical question.
			Specificity	89.9%
			Positive Predictive Value	61.7%
			Negative Predictive Value	50.2%
			Likelihood Ratio	1.6
Ward, C., et al 1996 UK	40 patients >60 of age were recruited after presenting to a morning clinic with a diagnosis of orthostatic hypotension. All patients were then seen three times for either a standing BP, or tilt table test.	Prospective cohort study	Reproducibility of standing BP test in diagnosing orthostatic hypotension	56.5%	Aim of the study not in line with the what clinical question is asking, and so the results are not presented in the most suitable fashion, but they are still of some interest. No reference to statistical power. No reference to ethical approval.
			Reproducibility tilt table test in diagnosing orthostatic hypotension	60%

Comment(s)

There is only one totally relevant study, and it scores well in critical appraisal. The data it provides is convincing in demonstrating a poor ability to diagnose orthostatic hypotension. Despite the lack of power calculation, a reassuringly large sample size was used, and the authors are convincing that had it been a prospective study, the outcomes would have been much the same. That said, it would have been preferable to blind the investigators to remove potential bias had it been prospective. There was also a study found that was investigating a different aspect of orthostatic hypotension, but it is possible to glean from their results that perhaps the two tests are comparable. Unfortunately because this paper does not score as well as first, and there was no other evidence found to back it up, it is not as persuasive as the first paper. It is possible to suggest from the results that lying and standing BP has a role in ruling out orthostatic hypotension. Further studies, especially those that investigate lying and standing rather than sitting and standing, would be useful to confirm this.

Clinical Bottom Line

Lying and standing BP is not suitable for the diagnosis of orthostatic hypotension.

References

1. Cooke, J., Carew, S., O'Connor, M., et al. Sitting and standing blood pressure measurements are not accurate for the diagnosis of orthostatic hypotension Q J Med 2009; 335-339
2. Ward, C., Kenny, R. Reproducibility of Orthostatic Hypotension in Symptomatic Elderly. Am J Med 1996; 418-422