[Diagnosis of pleural effusion in intensive care patients with supine digital thoracic imaging. A study of CT validated cases].

PURPOSE: The significance of the recumbent chest x-ray using digital luminescence radiography was to be assessed in respect of diagnosis of pleural effusions.

MATERIAL AND METHODS: Three experienced radiologists evaluated 32 digital recumbent chest x-rays of 32 intensive-care patients. The radiologists were asked to estimate the effusion volume and to assess whether typical x-ray signs of pleural effusions were seen. These evaluations were compared with one another and with the simultaneously produced CTs.

RESULTS: Diagnostic accuracy of the digital recumbent chest x-ray is of medium quality in respect of diagnosis of pleural effusions (sensitivity: 69%, specificity: 54%, positive predictive value: 81%, negative predictive value: 34%, rate of accuracy: 65%). Diagnostic safety is the same for right-sided or left-sided pleural effusions, and increases with increasing effusion volume. The ratings by the radiologists are statistically not significantly different, but are significantly different from the CT measurements (Wilcoxon test, p < 0.05). Correlations of the assessments and the measurements were weakly positive (r = 0.24, r = 0.36, r = 0.47). The pleural effusions were on the average underestimated by the radiologists. The median predictive error was 203 ml.

CONCLUSIONS: Recumbent chest x-ray with digital luminescence radiography is an imaging method of limited accuracy in respect of diagnosis of pleural effusions. Supplementary diagnostic methods are recommended, as the present results show, especially in such cases where the recumbent chest x-ray does not reveal an effusion or if the volume must be determined accurately. Digital recumbent chest x-ray ranks equal with conventional x-ray in the diagnosis of pleural effusions.