Evaluating diagnostic tests in the pleural space. Differentiating transudates from exudates as a model.

Physicians have a staggering variety of diagnostic tests available for directing their diagnostic and therapeutic decisions. Technologic advances in laboratory science have increased the sophistication of new tests and accelerated their rate of adoption into clinical practice. Unfortunately, studies that report the value of new diagnostic tests often fail to follow accepted methodologic standards for unbiased test assessment or provide clinicians with sufficient information for the intelligent evaluation of a test's performance and applicability. The following review of pleural fluid tests that discriminate between exudative and transudative effusions serves to highlight important methodologic considerations in the assessment of diagnostic tests.