Treating influenza in the emergency department.

The C d i f o d a Journd of Emergency Medicine U:1, January 201 page 4 a lab adjacent to the ED. Several disadvantages to performing these rapid diagnostic tests include the cost of the laboratory personnel to perform the lest, the actual cost of the test itself, and the fact that the test may miss many patients who actually have influenza A or B. Test sensitivities are generally in the 60.70% range. Recently, the FDA waived Federal CLIA requirements and approved an actual ten minute QuickVue bedside test with 7080% sensitivity. Because of cost, availabity. and sensitivity issues most EM physicians diagnose influenza on clinical criteria alone. Treatment. Prevention is the mosteffeciwe treatment as with other diseases. The CDC has published recommendations for high risk groups who should be vnccinaled, which includes all health care personnel.' Amantadme and rimantadine have been approved for use against influenza A for many years. These have generally not been popularly used in EDs. Disadvantages of these drugs includes lack of efficacy against influenza B, potential side effects, and rapid development of viral resistance. Two new drugs have been marketed for treatment of influenza A and B recently. These are the neurminidase inhibitors, oseltnmivir and zanamivir. Oseltamivir is taken orally. 75 mg twice and zanamivir via an inhalation appnratus, lOmg twice a day? Multiple studies bave demon- s m e d their efficacy. These agents work by inhibiting influenzavirus neuraminidase, aglyco-protein spike on the outside of the virus envelope needed for successful cellular release and transmission within the body. These new agents need to be administered within 36 houn of onset of symptoms to be effective. Recent studies also show efficacy in the prophylactic use in preventing influenza A and B, an exciting expansion in use of these agents. The prophylactic dose is one-half the acute dose. There are several advantages to neuraminidase inhibitors compared with amantadine including less evolution of resistance, efficacy against influenza B. dramatic reduction in symptom, even in patients who do have a full course of flu, and fewer side effects. In a study of 445 patients by the Mist group 1, zanamivir was given to The one-half and placebo to the others wirhin 36 hours of symptom o n s e ~ ~ dmtion of the flu was reduced by 1.5 days in normal groups and 2.5 days in high risk groups. A significantdecrease in the severity of illness in patients @eatedwith zanamivir allowed them to resume normal activities much swner. A recent study by Treanor compared areltamivir to placebo? lhis analysis included both with laboratory diagnoses of influenzaas well as those with only clinical diagnoses bosed on symptoms. A total of 629 subjects were enrolled and randomized into one of three ueatment arms: standard dose oseltamivir, high dose oseltamivir, and placebo. In both oseltamivirgroups the mean illness duration was reduced from 103 to 70 hours. The symptom severity decreased in the mated group by 40%. Additional studies analyzed the effect of neuraminidase inhibitors both in acute disease as well as in prevention.' In one of these studies, 837 relatives of sick family members who developed influenza were treated prophylactically with either placebo or zanamivic W e 20% of the placebo group became ill, only 4% of the drug-treated group became ill. In addition, this study also provided treament lo the index case family member and this resulted in a 2,.5day reduction in illness over placebo. DNA viral sequences were performed in this study and no mislant flu strains developed. A novel study analyzed the effects of oscllamivir in human volunteers in an experimentally induced influenza9 In aconmlled laboratory environment, these volunteers were directly inoculated inmasally with influenzaA: Texas 36/91 H h T One group had osellamivir begun 26 hours before virus inoculation and another group 28 hours after inocula- tion. In the propbylactic group, 38% of patients developed influenza compared with 67% of placebo. In the past-treatment group, the d m i o n of illness was reduced h m 95 hours to 53 hours and the severiy was reduced by 50% compared to placebo. INFECTIOUS DISE.4SES TREATLUG INFLUENZA IN THE E.MERGENCY DEPARTMENT Roben. W. Derlet MD UC Davis School of Medicine Patients frequently present to the emergency department (ED) with symptoms of influenza, the common cold, or a confusine combination of both svmotoms. As most California emergency physicians know, these symptoms appear more frequently in the winter months when large sections of ED waiting rooks may be filled with flu or UIU patients It is sometimes difficult to distineuish between influenza and the common cold. Influenza A and 6 are caused by an onhomyxovirus, whereas symptoms of the common cold can be caused by one of many viruses including rhinovirus, coronaviruses. RSV or adenovh.' Influenw A is a zoonotic infection thu also infecis oies. birds. horses, and seals. Indeed, the severe 1918 pandemic that resulted in millions of deaths worldwide is believed to bave originated from pigs.' Pinmosis: The following table has been utilized in some EDs to help discriminate between influenza and the common cold: I Onset Headache Rhinitis 1 Abmot I 100-104~~ Common I Common I Occasional 1 Gradual I IOD'F or ~ e s s 1 Occasional 1 Variable ..--- I I common The specificity and sensitivity of the above table have never been scientifically tested. Accurately diagnosing influenza A orB may be more difficult than the table above suggests. In addition to overlapping symptoms caused by URI and Cold viruses, other viruses cause influenza-like symptoms including enterovi- ruses, paramyxoviruses, and even tropical fevers such as Dengue. For example. 98% of persons who acquired West-Nile fever in New York in 1999 were initially diagnosed as having the flu. The gold standard fbr diagnosing influenza A and B is a viml culture of nasal-pharyngeal and/or ihroac samples using dacron swabs which need to be sent in appropriate viral transport media (eg. M4 T m p o r t Media) to the lab where it is cultured in several lines of cells. Diagnosis of influenzais made in the lab once specific cytopathic effect is observed or hemadsorption testing is positive. Confimtion is then performed using the infected cultured cell lines by staining them with fluorescent antibody. The process may tske from three to seven days: long after the patient has left the ED and well past the time when drug therapy could be efficacious. Dict.immunofluorexent tests on fresh specimens are also available in some labs, but are labor intensive and have sensitivity lower than culture methods. These tests require specially trained lab personnel far interpretation, not generally available all shifts, even in large medical centers. In order to overcome ~ & obstacle, several bedside tesu s have become available. In reality, many of these are not bedside tests as they generally require 30.60 minutes of time to perform multiple steps to complete the test,? Rapid tests are best done by