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Rapid flu tests, ICU delirium risk, and more.


Rapid flu tests accurate making diagnosis, but not ruling it out

Rapid influenza diagnostic tests (RIDTs) were more accurate at diagnosing the flu than ruling it out in a recent study, indicating that patients with a negative result would need additional testing.

Researchers reviewed 159 published studies to determine the accuracy of RIDTs in diagnosing flu in adults and children presenting with flu-like symptoms. RIDTs were defined as any commercially available assay that identified flu antigens or neuraminidase activity in respiratory specimens through simple immunochromatographic formats. In all studies, RIDTs were tested against one of two accepted reference standards. Results appeared in the April 3 Annals of Internal Medicine.

Specificity was more consistent across studies than sensitivity, with specificity estimates ranging from 50.5% to 100% and sensitivity estimates ranging from 4.4% to 100%. For all RIDTs, the pooled sensitivity from bivariate random-effects regression was 62.3% (95% CI, 57.9% to 66.6%) and the pooled specificity was 98.2% (95% CI, 97.5% to 98.7%). This corresponds to a positive likelihood ratio of 34.5 (95% CI, 23.8 to 45.2) and a negative likelihood ratio of 0.38 (95% CI, 0.34 to 0.43).

Subgroup analyses showed a higher pooled sensitivity in children (66.6%; 95% CI, 61.6% to 71.7%) compared with adults (53.9%; 95% CI, 47.9% to 59.8%; P<0.001). Pooled sensitivity differences between children and adults remained statistically significant when adjusted for brand of RIDT, specimen type or reference standard. Virus type also had an effect on the accuracy of RIDTs. The tests had better sensitivity for detecting influenza A (64.6%; 95% CI, 59.0% to 70.1%) than influenza B (52.2%; 95% CI, 45.0% to 59.3%; P=0.05).

The authors noted that a positive test is unlikely to be a false-positive result, allowing clinicians to confidently diagnosis and treat the flu.

“RIDTs fill a void at the point of care that no other test is likely to fill in the near future: as a first-line test to be confirmed (especially if negative) by more time-consuming, definitive testing,” they wrote. “As long as clinicians understand the limitations of RIDTs, namely that a negative result is unreliable and should be confirmed by using culture or RT-PCR [reverse transcription polymerase chain reaction], RIDTs could enable clinicians to institute prompt infection-control measures, begin antiviral treatment in high-risk populations, and make informed decisions about further diagnostic investigations.”

A second meta-analysis published in Annals concluded that oral oseltamivir and inhaled zanamivir may provide a net benefit over no treatment for influenza, although quality of evidence was low due to study designs.

Oral oseltamivir compared with no treatment may reduce mortality in high-risk populations (odds ratio [OR], 0.23; 95% CI, 0.13 to 0.43), hospitalization (OR, 0.75; 95% CI, 0.66 to 0.89) and duration of symptoms (33 hours; 95% CI, 21 to 45 hours). For every 1,000 patients, approximately 12 patients require hospitalization, and oral oseltamivir treatment can reduce this by 3 to 9 per 1,000 patients. Earlier treatment with oseltamivir was generally associated with better outcomes.

Inhaled zanamivir led to shorter symptom duration (23 hours; 95% CI, 17 to 28 hours) and fewer hospitalizations (OR, 0.66; 95% CI, 0.37 to 1.18) but more complications than no treatment. Direct comparison of oral oseltamivir and inhaled zanamivir does not suggest important differences in key outcomes, the authors said.

Although there is low to very low confidence in the estimates of effect, these findings must be viewed in the context of randomized controlled trials and “the substantial burden of influenza disease worldwide,” the authors wrote.

“The potential positive effect of earlier rather than later administration of oseltamivir on death in hospitalized patients and suggestions that pregnant women, children and patients who are immunocompromised may also benefit from treatment are among the key contributions of our study,” they wrote. “In addition, we found moderate quality evidence for the reduction in signs and symptoms from treatment with inhaled zanamivir compared to no treatment.”

Model predicts ICU delirium risk

A simple model outperforms clinicians at predicting which intensive care unit (ICU) patients are likely to develop delirium during their ICU stay, a study found.

Dutch researchers developed the PREdiction of DELIRium in ICu patients (PRE-DELIRIC) model using 1,613 adult ICU patients in one hospital, and temporally validated it with 549 patients at the same hospital. Data were collected from 894 additional patients from four other hospitals, for external validation. The model comprises 10 risk factors that are available within 24 hours of ICU admission: age, Acute Physiology and Chronic Health Evaluation (APACHE)-II score, admission group, coma, infection, metabolic acidosis, use of sedatives and morphine, urea concentration and urgent admission. The main outcome was development of delirium during a patient's ICU stay, with delirium defined as a minimum of one positive screening on the Confusion Assessment Method-Intensive Care Unit (CAM-ICU) or, in some cases, positive screening via the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV. Results were published Feb. 9 in BMJ.

Of the 1,613 original patients, 25.5% developed delirium; of the 549 temporal validation patients, 31.1% developed delirium. The prediction model had an area under the receiver-operating characteristic curve (AUROC) of 0.87. Temporal and external validation resulted in AUROCs of 0.89 and 0.84; the pooled AUROC was 0.85. The AUROC was significantly lower at 0.59 for both physicians' and nurses' predictions (n=124 patients), indicating the model was better at predicting delirium than clinicians. There were no differences in prediction between ICU nurses and student ICU nurses, or among predictions made by intensivists, intensivist fellows, or residents.

Though several prediction models exist for non-ICU patients and for older medical ICU patients, this is the first evidence-based prediction model for general ICU patients, the authors noted. Predicting delirium in ICU patients “facilitates the use of non-drug preventive measures in high-risk patients, such as improvement of orientation, cognitive stimulation, early mobilization, and listening to music,” the authors wrote, as well as drug interventions like prophylactic haloperidol. The optimal cut-off point of the model and the most effective delirium preventive interventions still need more study, they noted.

The model is available online.

Updated guidelines on thrombosis prevention, antithrombotic use

The American College of Chest Physicians recently released updated guidelines on antithrombotic therapy and prevention of thrombosis.

The new guidelines are an update of the organization's previous edition, which was published in 2008, and differ in several important ways, according to the authors. For example, the new guidelines are the first version to account for asymptomatic screening-related thrombosis, as well as the first to perform a systematic review of patients' preferences for treatment. In addition, each panel of experts included a practicing clinician who was not involved in research, with the goal of making the recommendations more useful in clinical practice. Input on appropriate resource use was also sought from experts in the field when determining the strength or weakness of recommendations.

The guidelines, which appeared as a supplement to the February Chest, cover the following areas of prevention, diagnosis and treatment in extensive detail: evidence-based management of anticoagulant therapy; prevention of venous thromboembolism (VTE) in nonsurgical patients, nonorthopedic surgical patients and orthopedic surgery patients; perioperative management of antithrombotic therapy; diagnosis of deep venous thrombosis; antithrombotic therapy for VTE disease, atrial fibrillation and peripheral artery disease; treatment and prevention of heparin-induced thrombocytopenia; antithrombotic and thrombolytic therapy for valvular disease and ischemic stroke; primary and secondary prevention of cardiovascular disease; VTE, thrombophilia, antithrombotic therapy and pregnancy; and antithrombotic therapy in neonates and children.

Not all doctors fully disclose errors, pharma ties, survey finds

A significant proportion of physicians do not completely agree that they should disclose serious medical errors or financial relationships with drug and device companies to patients, according to a recent survey. In addition, one-tenth of survey respondents had told patients something that was not true in the previous year.

Researchers surveyed 1,891 physicians in internal medicine, family practice, pediatrics, cardiology, general surgery, anesthesiology and psychiatry nationwide in 2009 to find out if they followed the standards on communication laid out by the American Board of Internal Medicine Foundation's Charter on Medical Professionalism. That charter was coauthored by the American College of Physicians and later endorsed by more than 100 groups worldwide, as well as the Accreditation Council for Graduate Medical Education. The survey excluded osteopaths, residents and those who practiced in federally owned hospitals. Results appeared in the February 2012 Health Affairs.

Nearly 20% of physicians said they had not fully disclosed an error to a patient in the previous year because they feared the admission would trigger a malpractice case. More than 55% of physicians said they rarely, sometimes, or often described a patient's prognosis in a more positive manner than warranted and 35% did not completely agree that they should disclose all financial ties with drug- and devicemakers to patients.

Women were more likely to report fully describing benefits and risks, disclosing financial relationships, and never having told an untruth to patients in the prior year. Underrepresented minorities were more likely than white or Asian respondents to report attitudes consistent with the charter.

General surgeons and pediatricians were most likely to completely support disclosing all serious medical errors to patients, while cardiologists and psychiatrists were least likely (P<0.001). Anesthesiologists, general surgeons and pediatricians were most likely to report never having described patients' prognoses in more positive terms than warranted, while internists and psychiatrists were least likely (P<0.05).

Cardiologists and general surgeons were most likely to report never having told patients an untruth in the previous year, while pediatricians and psychiatrists were least likely (P<0.001). Physicians in universities or medical centers were more likely to completely agree with the need to report all serious medical errors than physicians in solo or two-person practices (78.1% vs. 60.5%; P=0.03).

Even though the survey was anonymous, it likely underestimated the rate at which physicians do not comply with the professionalism charter, the study authors speculated.

“The survey results suggest that many physicians do not completely support the charter requirements related to communication with patients. An alternative interpretation is that treating support for the charter precepts as ‘black or white’—physicians either do or do not completely endorse and adhere to these principles—fails to recognize complexities of patient-physician communication in everyday practice,” they wrote.