To assess the diagnostic value of one rapid influenza diagnostic test used in this setting every winter, the investigators studied 764 patients younger than age 5 years who were admitted to the ED during four consecutive flu seasons with fever of unknown origin. The prevalence of influenza varied widely during the study period, from a low of 30% to a high of 62%.
The rapid diagnostic test performed comparably well across the four flu seasons, with only a modest decrease in sensitivity and specificity during the 2010 H1N1 flu pandemic. The bedside test had an overall sensitivity of 0.82, a specificity of 0.98, a positive likelihood ratio of 37.8, and a negative likelihood ratio of 0.19. These results are similar to those of two previous small-scale studies that found sensitivities of 69% to 85% and specificities of 83% to 98%, Dr Avril and associates said.
These findings “support the rational use of rapid influenza diagnostic tests in clinical practice for young children presenting with fever without a source during flu season,” the investigators said.
Dr Avril and associates added that they assessed only one rapid diagnostic test for influenza (QuickVue)—the only one available in their ED because of cost—but that there are 22 such tests commercially available. The QuickVue test is available in the United States.
1. Avril E, Lacroix S, Vrignaud B, et al. Variability in the diagnostic performance of a bedside rapid diagnostic influenza test over four epidemic seasons in a pediatric emergency department. Diag Microbiol Infect Dis. 2016. doi:10.1016/j.diagmicrobio.2016.03.015.
Zika Caused Rash, Pruritus More than High Fever
BY AMY KARON
FROM PLoS NEGL TROP DIS and EMERG INFECT DIS
Zika virus infection in adults often causes pruritic maculopapular rash, but rarely leads to clinically significant fever, according to two cohort studies in Rio de Janeiro. The findings raise questions about case definitions of Zika virus disease (ZVD). Currently, the interim case definition from the World Health Organization defines a suspected ZVD case as rash, fever, or both, plus at least one of three other symptoms—arthralgia, arthritis, or conjunctivitis.
“In our opinion, pruritus, the second most common clinical sign presented by the confirmed cases, should be added to the Pan American Health Organization case definition [for ZVD], while fever could be given less emphasis,” Dr Patricia Brasil of the Oswaldo Cruz Foundation in Rio de Janeiro and her associates wrote online in PLoS Neglected Tropical Diseases.1
Watching for a combination of itching and rash also could help distinguish ZVD from infections of Chikungunya and Dengue, co-circulating arboviruses in Brazil that tend to cause nonpruritic rash, the investigators noted. Distinguishing these infections is crucial because Dengue, in particular, can be devastating without appropriate treatment.
Brazil confirmed ZVD in the northeastern state of Bahia in May 2015. Cases in Rio de Janeiro soon followed, triggering worries because of its dense population and status as host of the 2016 Olympic and Paralympic Games. To better characterize ZVD in Rio de Janeiro, Dr Brasil and associates studied 364 cases of acute rash, with or without fever, among adults with clinical onset during the first half of 2015. Quantitative reverse transcription–polymerase chain reaction detected Zika viral RNA in blood samples from 119 (45%) of 262 patients tested.
The first 4 days of confirmed ZVD were marked by rash (97%), itching (79%), prostration (73%), headache (66%), arthralgias (63%), and myalgia (61%). Just 36% of patients were febrile, and fevers usually were short-lived and low-grade, in contrast to other arboviral infections. Partial sequencing of the Zika virus gene from 10 randomly selected positive samples showed that it resembled Asian strains of Zika virus, supporting the hypothesis that Pacific Islanders brought Zika to Rio de Janeiro during a canoe championship in 2014, the researchers added.
The researchers also determined that Zika virus was circulating in Rio de Janeiro as early as January 2015—“at least 5 months before its detection was announced by the health authorities, which must be taken into consideration for future design and implementation of effective syndromic surveillance systems,” they wrote. Surprisingly, an assay for Dengue was negative in all 250 patients tested, which might indicate “explosive transmission dynamics of ZVD,” the investigators added.
A retrospective cohort study of confirmed Zika virus cases in Rio de Janeiro also reported a much higher prevalence of rash compared with fever.2 This was a retrospective convenience sample of 57 patients, including 98% with rash, 56% with pruritus, and 67% with measured or self-reported fever. Most fevers were low-grade, and the median recorded temperature was 30.0°C (within normal limits). Other common presentations included headache (67%), arthralgias (58%), myalgias (49%), and joint swelling (23%), according to Dr Jose Cerbino-Neto of the Oswaldo Cruz Foundation in Rio de Janeiro and associates. Their findings support emphasizing rash, fever, or both as “primary characteristics” of ZVD, they added.