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The main objective of this study was to estimate the performance, under local epidemiological conditions, of two in-house ELISA assays for the combined detection of anti-SARS-CoV-2 IgA, IgM, and IgG immunoglobulins. A total of 94 serum samples were used for the assessment, where 44 corresponded to sera collected before the pandemic (free of SARS-CoV-2 antibodies), and 50 sera were collected from confirmed COVID-19 patients admitted to the main public hospital in the city of Valdivia, southern Chile. The Nucleocapsid (Np) and the receptor-binding domain (RBD) proteins were separately used as antigens (Np and RBD ELISA, respectively) to assess their diagnostic performance. A receiver operating characteristic (ROC) analysis was performed to estimate the optical density (OD) cut-off that maximized the sensitivity (Se) and specificity (Sp) of the ELISA assays. Np ELISA had a mean Se of 94% (95% CI = 83.5-98.8%) and a mean Sp of 100% (95% CI = 92.0-100%), with an OD 450 nm positive cut-off value of 0.88. On the other hand, RBD ELISA presented a mean Se of 96% (95% CI = 86.3-99.5%) and a mean Sp of 90% (95% CI = 78.3-97.5%), with an OD 450 nm positive cut off value of 0.996. Non-significant differences were observed between the Se distributions of Np and RBD ELISAs, but the latter presented a significant lower Sp than Np ELISA. In parallel, collected sera were also analyzed using a commercial lateral flow chromatographic immunoassay (LFCI), to compare the performance of the in-house ELISA assays against a commercial test. The LFCI had a mean sensitivity of 94% (95% CI = 87.4-100%) and a mean specificity of 100% (95% CI = 100-100%). When compared to Np ELISA, non-significant differences were observed on the performance distributions. Conversely, RBD ELISA had a significant lower Sp than the LFCI. Although, Np ELISA presented a similar performance to the commercial test, this was 2.5 times cheaper than the LFCI assay (labor cost not considered). Thus, the in-house Np ELISA could be a suitable alternative tool, in resource limited environments, for the surveillance of SARS-CoV-2 infection, supporting further epidemiological studies.

The aim of the study was to determine the longitudinal validity, reproducibility, responsiveness and interpretability of the adult version of the Brisbane Burn Scar Impact Profile, a patient-report measure of health-related quality of life.A prospective longitudinal cohort study of patients with or at risk of burn scarring was conducted at three assessment points (at baseline around the time of wound healing, one to two weeks post-baseline and 1-month post-baseline). Participants attending a major metropolitan adult burn centre at baseline were recruited. Participants completed the Brisbane Burn Scar Impact Profile and the 36-item Short Form Health Survey and Patient Observer Scar Assessment Scale. Intraclass Correlation Coefficients (ICCs), smallest detectable change, percentage of those who improved, stayed the same or worsened and Area under the Receiver Operating Characteristic Curve (AUC) were used to test the aim.Data were included for 118 participants at baseline, 68 participants at one to two weeks and 57 participants at 1-month post-baseline. All groups of items had acceptable reproducibility, except for the overall impact of burn scars (ICC = 0.69), the impact of sensations which was not expected to be stable (ICC = 0.63), mobility and daily activities (ICC = 0.63, 0.67 respectively). The responsiveness of six out of seven groups of items able to be tested against external criterion was supported (AUC = 0.72-0.75). Hypothesised correlations of changes in the Brisbane Burn Scar Impact Profile items with changes in criterion measures generally supported longitudinal validity (e.g., nine out of thirteen hypotheses using the SF-36 as an external criterion were supported). Internal consistency estimates, item-total and inter-item correlations indicated there was likely redundancy of some groups of items, particularly in the relationships and social interaction, appearance and emotional reactions items (Chronbach's alpha range = 0.94-0.95).Support was found for the reproducibility, longitudinal validity, responsiveness and interpretability of most groups of Brisbane Burn Scar Impact Profile items and some individual items in the test population. Potential redundancy of items should be investigated further.