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Background: One of the most challenging practical and daily problems in intensive care medicine is the interpretation of the results from diagnostic tests. In neonatology and pediatric intensive care the early diagnosis of potentially life-threatening infections is a particularly important issue. Focus: A plethora of tests have been suggested to improve diagnostic decision making in the clinical setting of infection which is a clinical example used in this article. Several criteria that are critical to evidence-based appraisal of published data are often not adhered to during the study or in reporting. To enhance the critical appraisal on articles on diagnostic tests we discuss various measures of test accuracy: sensitivity, specificity, receiver operating characteristic curves, positive and negative predictive values, likelihood ratios, pretest probability, posttest probability, and diagnostic odds ratio. Conclusions: We suggest the following minimal requirements for reporting on the diagnostic accuracy of tests: a plot of the raw data, multilevel likelihood ratios, the area under the receiver operating characteristic curve, and the cutoff yielding the highest discriminative ability. For critical appraisal it is mandatory to report confidence intervals for each of these measures. Moreover, to allow comparison to the readers' patient population authors should provide data on study population characteristics, in particular on the spectrum of diseases and illness severity.

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The daily risk for pneumonia decreases with increasing duration of stay in the intensive care unit. Witnessed aspiration and exposure to paralytic agents are potentially modifiable independent risk factors. Exposure to antibiotics was associated with low rates of early ventilator-associated pneumonia, but this effect attenuates over time.

Clinical decisions should be based on the totality of the best evidence and not the results of individual studies. When clinicians apply the results of a systematic review or meta-analysis to patient care, they should start by evaluating the credibility of the methods of the systematic review, ie, the extent to which these methods have likely protected against misleading results. Credibility depends on whether the review addressed a sensible clinical question; included an exhaustive literature search; demonstrated reproducibility of the selection and assessment of studies; and presented results in a useful manner. For reviews that are sufficiently credible, clinicians must decide on the degree of confidence in the estimates that the evidence warrants (quality of evidence). Confidence depends on the risk of bias in the body of evidence; the precision and consistency of the results; whether the results directly apply to the patient of interest; and the likelihood of reporting bias. Shared decision making requires understanding of the estimates of magnitude of beneficial and harmful effects, and confidence in those estimates.

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We compared the diagnostic efficacy of fractionated plasma metanephrine measurements to measurements of 24-h urinary total metanephrines and catecholamines in outpatients tested for pheochromocytoma at Mayo Clinic Rochester from January 1, 1999, until November 27, 2000. Catecholaminesecreting tumors were histologically proven. The sensitivity of fractionated plasma metanephrines was 97% (30 of 31 patients), compared with a sensitivity of 90% (28 of 31) for urinary total metanephrines and catecholamines (P = 0.63). The specificity of fractionated plasma metanephrines was 85% (221 of 261), compared with 98% (257 of 261; P < 0.001) for urinary measurements. The likelihood ratios for positive tests were 6.3 (95% confidence interval, 4.7 to 8.5) for fractionated plasma metanephrines and 58.9 (95% confidence interval, 22.1 to 156.9) for urinary total metanephrines and catecholamines. An adrenal pheochromocytoma was missed by urinary testing in two patients with familial syndromes and one asymptomatic patient with an incidentally discovered adrenal mass. An extra-adrenal paraganglioma was missed by plasma testing in one patient. In conclusion, measurements of 24-h urinary total metanephrines and catecholamines yield fewer false-positive results, an attribute preferred for testing low-risk patients, but fractionated plasma metanephrine measurements may be preferred in high-risk patients with familial endocrine syndromes.

Use of composite end points as the main outcome in randomised trials can hide wide differences in the individual measures. How should you apply the results to clinical practice? Improvements in medical care over the past two decades have decreased the frequency with which patients with common conditions such as myocardial infarction develop subsequent adverse events. Although welcome for patients, low event rates provide challenges for clinical investigators, who consequently require large sample sizes and long follow up to test the incremental benefits of new treatments. Clinical trialists have responded to these challenges by relying increasingly on composite end points, which capture the number of patients experiencing any one of several adverse events-for example, death, myocardial infarction, or hospital admission. 1 Use of composite end points is usually justified by the assumption that the effect on each of the components will be similar and that patients will attach similar importance to each component. 1 But this is not always the case. In this article we provide a strategy to interpret the results of clinical trials when investigators measure the effect of treatment on an aggregate of end points of varying importance. Example caseConsider a 76 year old man who has disabling angina despite taking blockers, nitrates, aspirin, an angiotensin converting enzyme inhibitor, and a statin. His doctor suggests cardiac catheterisation and possible revascularisation. The patient is reluctant to have invasive management, and wonders how much benefit he might expect from surgery.The trial of invasive versus medical therapy in elderly patients (TIME) is relevant. 2 The study randomised 301 patients aged 75 years or older with resistant angina to optimised drug treatment or cardiac catheterisation and possible revascularisation. Although the groups showed no difference in quality of life at 12 months, the frequency of a composite end point (death, non-fatal myocardial infarction, and hospital admission for acute coronary syndrome) was much lower in the revascularisation group (25.5%) than in the medical management arm (64.2%; hazard ratio 0.31, 95% confidence interval 0.21 to 0.45).Although the overall result suggests invasive treatment would be beneficial, marked differences existed in the absolute reduction in risk across components (table 1). In the invasive group, five more patients died but there were six fewer myocardial infarctions and 78 fewer hospital admissions. How should you interpret these results and inform the patient? Evaluating composite end pointsClinicians can use three questions to help decide whether to base a clinical decision on the effect of treatment on a composite end point or on the component end points (box). We will not expand on statistical issues here, but box A on bmj.com gives a brief outline. Importance of individual components to patientsWhen all components of a composite end point are of equal importance to the patient, it will not be misleading to assume that the effect of the int...