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

Transcription

1 Author s response to reviews Title: Accuracy and reliability of an NS1 rapid immunochromatographic test for DENV-1 diagnosis at point of care and in the laboratory Authors: Veronica Mata (veronica.mata@ini.fiocruz.br) Sonia Lambert Passos (sonia.lambert@ini.fiocruz.br) Yara Marques Hökerberg (yarahahr@ini.fiocruz.br) Guilherme Berardinelli (guilherme.berardinelli@ini.fiocruz.br) Maria Angelica dos Santos (angelicabsantos@ensp.fiocruz.br) Levy Boas Fukuoka (levyf@id.uff.br) Anna Carolina Rangel Maciel (annacarolinafontoura@gmail.com) Cintia Rodrigues (cintia_damasceno7@yahoo.com.br) Aline Santos (awvgsantos@gmail.com) Raquel Oliveira (raquel.vasconcellos@ini.fiocruz.br) Version: 1 Date: 07 May 2017 Author s response to reviews: Rio de Janeiro, May 7th, A/C Editor-in-Chief BMC Infectious Diseases Dear Dr Tang, We are submitting the revised version of our manuscript Accuracy and reliability of an NS1 rapid immunochromatographic test for DENV-1 diagnosis (INFD-D_17_00305). We thank for your thoughtful review and comments. Find below our point-by-point response to each reviewer/editorial point raised.

2 Reviewer 1: The potential use of Bioeasy TM NS1 antigen rapid immunochromatographic test as whole blood POC test for Dengue was assessed in this study. Overall, the study is written well. The discussion section could be strengthened. Thanks for your comments. We included sentences, supported by references, to strengthen the discussion on the following points: high specificity of ELISA Platelia in Dengue 1 [36]; and cocirculation and cross reactivity of Zika virus with IgM ELISA Dengue but not with ELISA NS1 [26]; [37]; Robustness of this result is strengthened by the use of composite reference test, comprising PCR Dengue [24] and ELISA Dengue NS1 Platelia. The latter has shown very high specificity (100%) in DENV-1 in a previous study.[36].lines Evidence for Zika and Dengue cross reactivity has, so far, been identified for IgM ELISA dengue but not for ELISA NS1 dengue tests [26, 37]. In our study, one of four Zika positive samples showed cross-reactivity with IgM Dengue ELISA, but none cross-react with NS1 ELISA Dengue. Increasingly acute febrile syndromes will demand investigation for several flaviviruses Lines Abstract conclusions- The authors conclude that the test is to be re-read in 30 minutes if invalid in 15 minutes, but the results section does not show evidence for this. Please, add this in the results. We added evidence on test result changes upon increasing reading times to the Results Section (lines ): For all the five invalid cases on readings performed at 15 minutes in whole blood at POC, readings repeated at 30 minutes tested positive. For two serum samples at the laboratory showing invalid readings at 15 minutes, one turned positive at 30 minutes and the other remained invalid (Figure 1). We also corrected Figure 1 to make this information clearer. Line 120- The informed consent is free? Yes, all patients signed a free and informed consent form. We included the word free on line 121. Lines Methods: Please confirm whether both tests were used as reference.

3 Yes, RT-PCR and PlateliaTM Dengue NS1 Ag-ELISA were used as reference tests. We changed lines to make this clearer as follows: All samples were tested using Reverse Transcription Polymerase Chain Reaction (RT-PCR) for dengue and PlateliaTM Dengue NS1 Ag-ELISA (Bio-RadTM Laboratories, France) as reference, performed according to the protocol described by Lanciotti et al. (1992) [24] and the manufacturer s specifications, respectively [25]. Dengue cases were defined by a positive result in at least one of them and non-dengue by negative results in both. Line 152- Does Zika cross react with Dengue testing. If so, please mention. We included a sentence in results section (lines ) to inform that there wasn t crossreaction with ELISA NS1 Dengue but One Zika Positive sample tested positive in IgM ELISA. We discussed this further in discussion section: Evidence for Zika and Dengue cross reactivity has, so far, been identified for IgM ELISA dengue but not for ELISA NS1 dengue tests [26, 37]. In our study, one of four Zika positive samples showed cross-reactivity with IgM Dengue ELISA, but none cross-react with NS1 ELISA Dengue. Increasingly acute febrile syndromes will demand investigation for several flaviviruses..(lines ). Lines Please reword the sentence or remove it. How was clinical severity measured? We changed the sentence on lines to inform that: None of the patients evidenced clinical severity signs according to WHO 2009 criteria [4]. We also added this information to the data collection section (line 120: according to WHO 2009 criteria for Dengue diagnosis [4, 23]. Reviewer 2: The manuscript submitted by Verónica Elizabeth Mata et al. is well written except for the correction suggested below Thanks for your comments. Revise line 33 to: A cross-sectional study in 144 adults with up to 4 d. This sentence was changed to: Cross-sectional study involving 144 adults spontaneously demanding care in an emergency department within 4 days of onset of acute febrile illness. (Lines 33-34). revise line 78 to: However, the sensitivity differs, ranging from 55.2 to 94.3%

4 This sentence on Lines was changed to: However, the sensitivity showed substantial discrepancy, ranging from 55.2% to 94.3% [10-11]. revise line 212 to :30-minute reading it varied from 78.3 to 84.9% The sentence on Lines was changed to: For the 30-minute reading, sensitivity was 78.3% using whole blood at point of care and 84.9% in serum in the laboratory (Table 1). revise line 213 to 214 to: reading varied from 87 to 100%, while that of the 30-minute reading varied from 87.5 to 95.8% This sentence was changed to: Specificity at 15-was 87% for whole blood at point of care and 100% for serum at the laboratory. For 30-minute readings, specificity was 87.5% for whole blood at point of care and 95.8% for serum in the laboratory. (Lines ). line 231: The statement " However, when 95% CI was analyzed, the reliability varied from to substantial to.." is not comprehensive please rephrase to include the missing information This sentence was changed to: However, considering the lower limit of Kappa 95% Confidence Interval, reliability interpretation decreased from almost perfect to substantial both for interobserver (0.73) and for intra-observer 0.75) (Table 2) (Lines ). Reference Section: We checked and corrected all REFERENCES as required a) Formats corrected for references 1,9,14,15,18,24,27, 29 b) Links corrected or included for references 4,5,13,25,34,35 c) Reference 32 is correct d) New references introduced: We replaced the original reference 3 with reference below and change text accordingly 3. Shepard DS, Undurradga EA, Halasa YA, Stanaway JD. The global economic buden of dengue: a systematic analysis. The Lancet Infectious Disease. 2016;16(8): Refs 36 and 37, included in the discussion section

5 36. Pal S, Dauner, AL, Mitra, I, Forshey, BM, Garcia, P, Morrison, AC, Halsey, ES, Kochel, TJ, Wu SJ. Evaluation of Dengue NS1 Antigen Rapid Tests and Elisa kits using clinical samples. PLoS One. 2014; 9(11): e Matheus S, Boukhari R, Labeau B, Ernault V, Bremand L, Kazanji M, Rousset D. Specificity of Dengue NS1 antigen in differential diagnosis of dengue and Zika Virus Infection. Emerg Infect Dis. 2016;22(9): We look forward to hearing from you soon, Sincerely. Verónica E. Mata