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Three Part Question

In [patients with chronic respiratory disease] does [V-Q scintigraphy have greater diagnostic utility than computed tomography] in the [investigation of pulmonary embolus]?

Clinical Scenario

A 70 year old known COPD patient presents to your emergency department with pleuritic chest pain and dyspnoea suggestive of pulmonary embolus. Initial investigations do not exclude pulmonary embolus. As part of your diagnostic strategy, you wonder if V-Q scintigraphy has better diagnostic utility than CT for pulmonary embolus.

Search Strategy

Medline 1966-07/03 using the OVID interface.
(exp Tomography, Spiral Computed OR exp Tomography, X-Ray Computed OR "CT".mp) AND (exp Ventilation-Perfusion Ratio OR "VQ".mp OR "V-Q".mp OR Ventilation Perfusion.mp OR Ventilation-Perfusion.mp OR perfusion.mp) AND (exp pulmonary embolism OR pulmonary embol$.mp OR "PE".mp OR Pulmonary infarct$.mp OR exp thromboembolism$ OR thromboembolism$.mp) LIMIT to human AND English.

Search Outcome

Altogether 239 papers found of which 238 did not address the exact question. One paper was of relevance.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Hartmann I et al, 2000, Netherlands	627 patients (91 COPD, 536 non-COPD) with suspected PE diagnosis PE Inclusion (angiography or high-probability V-Q) PE Exclusion (normal angiography or perfusion scintigraphy)	Diagnostic study	Proportion of diagnostic VQ scans and CT pulmonary angiograms from both groups	54% of VQ scans in COPD group ruled in/out PE vs 79% of VQ scans in non-COPD group	Observational groups not evenly matched Questional inclusion COPD criteria No power calculation
			Sensitivity and specificity of VQ and CT in both groups	All CT pulmonary angiograms gave a rule in/rule out result. No statistical diffence between the two groups

Comment(s)

Surprisingly few comparative studies. Ultimately small number studied in the study in question. Rigid definition of study population and reporter bias pose difficulties in such a study group. Diagnostic utility of V-Q questionable owing to high proportion of inconclusive results - resource & economic factors are thus of relevance.

Clinical Bottom Line

There is not enough evidence to support V-Q Scintigraphy as initial investigation of choice in COPD patients.

References

1. Hartmann I, Petronella H, Melissant C et al. Effect of Chronic Obstructive Pulmonary Disease on the Performance of D-Dimer Testing, Ventilation/Perfusion Scintigraphy, Spiral Computed Tomographic Angiography, and Conventional Angiography. Am J Crit Care Med 2000;162:2232-2237.