Pitfalls in acute febrile illness diagnosis: Interobserver agreement of signs and symptoms during a dengue outbreak.

AIMS AND OBJECTIVES: To compare and evaluate interobserver (nurses and physicians) agreement for dengue clinical signs and symptoms, including the World Health Organization diagnostic algorithm. BACKGROUND: Agreement of clinical history defines the capacity of the examiner to measure a given clinical parameter in a reproducible and consistent manner, which is prerequisite for diagnosis validity. Nurses play a major role in the triage and care of dengue patients in many countries. STUDY DESIGN: This is a sub-study on interobserver agreement performed as part of a cross-sectional diagnostic accuracy study for acute febrile illness (AFI) using the checklist STARD. METHODS: A previously validated semi-structured sign and symptom standardised questionnaire for AFI was independently administered to 374 patients by physician and nurse pairs. The interobserver agreement was estimated using kappa statistics. RESULTS: For a set of 27 signs and symptoms, we found six interobserver discrepancies (examiner detected red eyes, lethargy, exanthema, dyspnoea, bleeding and myalgia) as identified by regular and moderate kappa indexes. Four signs (patient observed red eyes, cough, diarrhoea and vomiting) and one symptom (earache) had near-perfect agreement. Most signs and symptoms showed substantial agreement. The WHO (Dengue guidelines for diagnosis, treatment, prevention and control: new edition, World Health Organization, 2009) clinical criteria for dengue comprise a group of symptoms known as "pains and aches." Interobserver agreement for abdominal pain, retro-orbital pain and arthralgia exceed that found for headache and myalgia. CONCLUSIONS: During a dengue outbreak, the interobserver agreement for most of the signs and symptoms used to assess AFI was substantial. RELEVANCE TO CLINICAL PRACTICE: This result suggests good potential applicability of the tool by health professionals following training. A well-trained health professional is qualified to apply the standardised questionnaire to evaluate suspected dengue cases during outbreaks.

Precisão e confiabilidade de um teste imuno-cromatográfico rápido NS1 para diagnóstico DENV-1 no ponto de atendimento e no laboratório.

BACKGROUND: Rapid immunochromatographic tests (ICT) for dengue non-structural protein 1 (NS1) have shown good performance for diagnosing acute-phase dengue in serum in laboratory settings, but rarely have been assessed in whole blood and at point of care (POC). This study compare the accuracy and inter- and intra-observer reliability of the NS1 Bioeasy™ ICT in whole blood at POC versus serum in the laboratory, during a DENV-1 epidemic. METHODS: Cross-sectional study involving 144 adults spontaneously demanding care in an emergency department within 4 days of onset of acute febrile illness. Accuracy of NS1 Bioeasy™ ICT was compared in whole blood and serum, both at 15 and 30 min, blinded to the reference RT-PCR or NS1 ELISA. Non-dengue patients were also tested for Zika virus with RT-PCR. Reliability of whole blood and serum readings by the same or different observers was measured by simple kappa (95% CI). RESULTS: At 15 min, sensitivity (Sn) of NS1 Bioeasy™ ICT in whole blood/POC was 76.7% (95% CI: 68.0-84.1) and specificity (Sp) was 87.0% (95% CI: 66.4-97.2). Sn in serum/laboratory was 82% (95% CI: 74.1-88.6) and Sp 100% (95% CI: 85.8-100). Positive likelihood ratio was 5.9 (95% CI: 2.0-17.0) for whole blood/POC and 19.8 (95% CI: 2.9-135.1) for serum/laboratory. Reliability of matched readings of whole blood/POC and serum/laboratory by the same observer (k = 0.83, 95% CI: 0.74-0.93) or different observers (k = 0.81, 95% CI: 0.72-0.92) was almost perfect, with higher discordant levels in the absence of dengue. Results did not differ statistically at 5%. CONCLUSIONS: NS1 Bioeasy™ ICT in DENV-1 epidemics is a potentially confirmatory test. Invalid results at 15 min should be reread at 30 min. To optimize impact of implementing ICT in the management of false-negatives it should be incorporated into an algorithm according to setting and available specimen. TRIAL REGISTRATION: UTN U1111-1145-9451 .

Correction to: Accuracy and reliability of an NS1 rapid immunochromatographic test for DENV-1 diagnosis at point of care and in the laboratory.

An error occurred during the publication of the original article [1].