A report in the February issue of PLoS Medicine has found that universal, year-round screening of donated blood for West Nile virus (WNV) is no more effective than only screening during the season when the virus is most likely to be transmitted. The authors suggest the optimal use of a state’s resources is to have screening policies based on duration and intensity of the regional epidemic.
Caroline T Korves and colleagues at the Harvard School of Public Health predicted the number of cases of WNV in three situations: high infection/long duration, high infection/short duration and low infection/short duration. Year-round screening did not prevent any more cases than seasonal (May–October) screening in any of these scenarios.
In areas of low transmission it was found that screening with a questionnaire alone was the most cost-effective alternative. Testing blood donations did not reduce the number of cases or increase quality-adjusted life year (QALY) expectancy.
Although blood screening reduced the number of cases and increased QALY expectancy in high-transmission regions, the study found that the most cost-effective strategy was to individually screen blood meant for transfusion of immunocompromised patients. Korves states that this is because these patients have a higher risk of becoming diseased from infection.
The report states that using a nucleic acid test to screen the entire donor pool would cost US$1.7 million per QALY gained. This is well beyond the accepted threshold for healthcare interventions of $50,000–100,000 per QALY. Seasonal screening of blood from immunocompromised patients has an incremental cost–effectiveness ratio of $56,000 per QALY gained, in line with the accepted threshold.
Inhaled recombinant insulin approved
Both the US FDA and the European Commission have approved an inhalable form of recombinant human insulin to control hyperglycemia in adults with type 1 and type 2 diabetes mellitus. Exubera® is the first noninjectable insulin to be approved in the USA. The manufacturers Pfizer Inc. expect the drug to be commercially available by mid 2006.
The approval came after evidence from clinical trials following over 2500 patients, with an average duration of 20 months, found that inhaled insulin had a similar efficacy to short-acting insulin in achieving glycemic control in adults with types 1 and 2 diabetes. The studies also demonstrated that glycemic control was improved for cases of type 2 diabetes that were not sufficiently controlled with standard oral treatments.
Most US influenza viruses resistant to adamantanes
A report by the Centers for Disease Control and Prevention in Atlanta has found that approximately 90% of influenza A virus isolated in the USA this season are resistant to the adamantane drugs rimantadine and amantadine.
Rick A Bright who led the investigation said, “These drugs should not be used for the treatment or prophylaxis of influenza in the USA until susceptibility to adamantanes has been re-established.”
The findings are based on an analysis of the viral M2 ion channel protein gene of isolates taken from 26 states between 1st October and 31st December 2005. When the vius binds to an adamantane drug this gene prevents the replication of the virus within infected cells. The S31N mutation confers resistance to this class of drugs.
The investigation found that 92.3% of H3N2 and 25% of H1N1 viruses had the drug-resistant mutation. The mutation was also found in all three samples of H1N1 from Canada and all ten isolates from Mexico. Similar increases in adamantane resistance can also be seen in Asia.
In a recent editorial, David M Weinstock and Gianna Zuccotti have attributed the marked increase in adamantane resistance in Asia to the over-the-counter availability of the drugs. More recently, fears of an Avian flu pandemic have led to inappropriate use of both rimantadine and amantadine. In Japan, resistance to neuraminidase inhibitors is also being observed.
Weinstock and Zuccotti argue that if the use of antivirals can be curtailed through, for example, education programs for patients, then susceptible strains may re-emerge.
Anticholinergic drugs associated with mild cognitive impairment in elderly
A study in the British Medical Journal has found that elderly patients using anticholinergic drugs are at increased risk of being diagnosed with mild cognitive impairment (MCI), although not at increased risk of dementia.
Marie L Ancelin and colleagues who carried out the studies state, “Not only do doctors commonly fail to associate cognitive dysfunction in elderly people with anticholinergic agents, they also underestimate anticholinergic toxicity, prescribing such drugs at high to excessive levels.” The report also warns of the dangers of unregulated toxicity due to the increasing number of anticholinergic drugs available without prescription.
The longitudinal cohort study followed 372 people aged over 60 years without dementia living in the Montpellier region of France. The primary end points were the anticholinergic burden from drug use, neurological assessment and cognitive examination.
9.2% of the subjects used anticholinergic drugs continuously for 1 year prior to cognitive assessment. Compared with nonusers, these subjects performed worse on tests of delayed nonverbal memory, attention, reaction time, language tasks, visuospatial recall and narrative recall. There were no differences between the two groups on tests of implicit memory, reasoning and immediate and delayed recall of word lists.
80% of the continuous users were diagnosed with MCI compared with 35% of nonusers, with anticholinergic drug use a strong predictor. Follow-up after 8 years found no difference between nonusers and users in the risk of developing dementia.
Based on this evidence the authors conclude that, “Doctors should assess current use of anticholinergic drugs in elderly people with mild cognitive impairment before considering administration of anticholinesterase inhibitors.”
Self-management of warfarin dose may reduce mortality
A meta-analysis reported in The Lancet has found that patients who self-manage warfarin dosing have fewer thromboembolic events and lower mortality.
C Heneghan and colleagues explained that, “When self-monitoring, the patient can either self-test and self-adjust treatment according to a predetermined dose schedule, or self-test and call a clinic to receive the appropriate dose adjustment.”
In 14 randomized trials of selfmonitoring, pooled estimates demonstrated significant reductions in major hemorrhage, thromboembolic events and all-cause mortality. Trials combining self-monitoring and self-adjusted therapy found significant reductions in death and thromboembolic events but not major hemorrhage.
Other advantages of self-monitoring include that it is more convenient for patients, allows more frequent monitoring and results in better treatment compliance. However, the authors note that self-monitoring is not suitable for all patients and requires the identification and education of those who may benefit.
Quicker test for avian flu in humans approved by FDA
A PCR-based test has been approved by the US FDA for diagnosing strains of avian flu in humans. The new test, which detects strains of H5 virus, provides preliminary results within 4 h. This is a great improvement on the 2–3-days wait necessitated by current diagnostic tests.
The Centers for Disease Control and Prevention developed the new test, called the influenza A/H5 (Asian lineage) virus real-time RT-PCR primer and probe set.
Mark Leavitt, the US Department of Health and Human Services (HSS) Secretary, said “The availability of this new test gives us one more tool to keep up with the ever-changing nature of influenza viruses.”
The HSS plans to distribute the test to 140 labs across all 50 states. It is believed this will enhance early detection and increase the response capacity of the labs.
Updated guidelines for use of oral appliances in sleep apnea
The American Academy of Sleep Medicine has updated the 1995 guidelines on the use of oral appliances (OAs) in the treatment of obstructive sleep apnea (OSA).
OSA affects approximately 18 million people in the USA and can lead to severe complications such as hypertension and coronary heart disease. However, Kent Moore, president of the Academy of Dental Sleep Medicine, says the condition can be eased with the use of OAs which “may control mild-to-moderate OSA with minimal discomfort or disruption”.
The guidelines make the new recommendation that OAs should be used by patients with mild-to-moderate OSA who prefer their use to treatment with continuous positive airway pressure (CPAP), or who are not good candidates for the latter type of treatment.
However, whenever possible, CPAP is advised for patients with severe OSA.
It is also recommended that patients treated with OAs have regular check-ups with the dental specialist, in order to monitor compliance and determine the integrity of the occlusion. Follow-up checks are also advised to ascertain whether the OSA is worsening.
The guidelines are designed for adults and adolescents, as literature on OSA in children is not well developed. They state that ultimate judgment on which treatment to use should rest with the clinician.
Conivaptan approved for euvolemic hyponatremia
The conivaptan HCI injection Vaprisol® has been approved by the US FDA for treatment of euvolemic hyponatremia in hospitalized patients.
The approval is based on evidence from a study in 56 patients with mild-to-moderate euvolemic hypontremia. The randomized, double-blind trial found hyponatremia was corrected in 66.7% of patients that used 40 mg of conivaptan per day for 4 days, compared with 28.6% of those recieving a placebo.
The most common adverse events were hypokalemia, thirst, headache, vomitting and infusion site reactions. Most were mild and did not lead to discontinuation. It is recommended to rotate the injection site every 24 h.