Performance of rubella suspect case definition: implications for surveillance.
OBJECTIVE
To assess the performance of the rubella suspect case definition among patients with rash diseases seen at primary care units.


METHODS
From January 1994 to December 2002, patients with acute rash, with or without fever, were seen at two large primary health care units and at a public general hospital in the municipality of Niterói, metropolitan area of Rio de Janeiro, Brazil. Data from clinical and serologic assessment were used to estimate the positive predictive values of the definition of rubella suspect case from the Brazilian Ministry of Health and other combination of signs/symptoms taking serologic status as the reference. Serum samples were tested for anti-rubella virus IgM using commercially available enzyme immunoassays. Positive predictive values and respective 95% confidence intervals were calculated.


RESULTS
A total of 1,186 patients with an illness characterized by variable combinations of rash with fever, arthropathy and lymphadenopathy were studied. Patients with rash, regardless of other signs and symptoms, had 8.8% likelihood of being IgM-positive for rubella. The Brazilian suspect case definition (fever and lymphadenopathy in addition to rash) had low predictive value (13.5%). This case definition would correctly identify 42.3% of the IgM-positive cases, and misclassify 26.1% of the IgM-negative cases.


CONCLUSIONS
These results support the recommendation to investigate and collect clinical specimens for laboratory diagnosis of all cases of rash, for surveillance purposes. Although this strategy may increase costs, the benefits of interrupting the circulation of rubella virus and preventing the occurrence of congenital rubella syndrome should pay off.
de Oliveira
Solange Artimos
SA
Disciplina de Doenças Infecciosas e Parasitárias, Hospital Universitário Antonio Pedro, Niterói, RJ, Brasil. artimos@vm.uff.br
Camacho
Luiz Antonio Bastos
LA
de Medeiros Pereira
Antonio Carlos
AC
Bulhões
Marília Mattos
MM
Aguas
Angélica Fortes
AF
Siqueira
Marilda Mendonça
MM
D000914:Antibodies, Viral / Q000097:blood*; D001938:Brazil; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007075:Immunoglobulin M / Q000097:blood*; D008297:Male; D011159:Population Surveillance; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012409:Rubella / Q000175:diagnosis*; D012412:Rubella virus / Q000276:immunology*; D012680:Sensitivity and Specificity
D000914:Antibodies, Viral; D007075:Immunoglobulin M; D011933:Reagent Kits, Diagnostic