Nguyen 2020.

Study characteristics
Patient Sampling	Purpose: Diagnosis of current acute‐phase infection or current convalescent phase infection Design: Single‐group study to estimate sensitivity only [1] Confirmed COVID cases (hospitalised, ICU) (n = 99) Recruitment: Not stated Prospective or retrospective: Prospective Sample size: 99 (99) Further detail: Inclusion: [1] ICU patients presenting with severe SARS‐Cov‐2 infection confirmed by routine RT‐PCR methodology Exclusions not stated
Patient characteristics and setting	Setting: Hospital inpatients (ICU) Location: AP.HP. Centre Cochin university hospital, ICU department, Paris, France CMC Ambroise Paré, ICU department, Neuilly‐sur‐Seine, France Country: France Dates: Not stated Symptoms and severity: ICU patients presenting with severe SARS‐Cov‐2 infection Demographics: Age: mean 62.4 (SD 13.3) years; 34 (34.3%) women; BMI: 29.1 ± 5.9 kg/m2 Chronic immunosuppression: 9 (9.1%) Exposure history: Not stated Non‐Covid group 1: NA Source: NA Characteristics: NA Non‐Covid group 2: NA Source: NA Characteristics: NA
Index tests	Test name: BIOSYNEX COVID‐19 BSS (IgG/IgM)® Manufacturer: Biosynex, Illkirch‐Graffenstaden, France Antibody: IgG/IgM Antigen target: Not stated Evaluation setting: POCT performed as POCT Test method: Lateral flow test (unspecified) Timing of samples: 17.9 ± 8.2 days since pso 0‐10 days: n = 18 11‐20 days: n = 45 21+ days: n = 35 1 sample unclear (only 98 samples in Fig. 1a) Samples used: Finger prick, with 10 μL of blood Test operator: Physicians Definition of test positivity: QC met and POCST showed no IgM and no IgG were considered negative. Positive: QC met and presence of IgM and/or IgG Blinding reported: no (only COVID cases, POCT) Threshold predefined: yes, visual‐based
Target condition and reference standard(s)	Reference standard: positive for SARS‐Cov‐2 using routine RT‐PCR methodology, threshold not stated Samples used: Not stated Timing of reference standard: Not stated Blinded to index test: Yes, prior to index test Incorporated index test: no Definition of non‐COVID cases: NA Samples used: NA Timing of reference standard: NA Blinded to index test: NA Incorporated index test: NA
Flow and timing	Time interval between index and reference tests: Not stated All patients received same reference standard: yes Missing data: yes, 1 sample seemed to be missing a result. Uninterpretable results: None. 2 (2.0%) in whom quality control was not met; hence, tests required to be performed twice. Indeterminate results: None (no indeterminate range) Unit of analysis: Patients
Comparative
Notes	Funding: No funding Biosynex which freely provided point‐of‐care serology tests Publication status: Published letter Source: Critical Care Author COI: All authors declared no conflict of interest regarding the content of this work. In particular, none had interests with BioSynex.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Was a case‐control design avoided?	No
Did the study avoid inappropriate exclusions?	Unclear
Did the study avoid inappropriate inclusions?	Unclear
Could the selection of patients have introduced bias?		High risk
Are there concerns that the included patients and setting do not match the review question?			High
DOMAIN 2: Index Test (All tests)
DOMAIN 2: Index Test (Antibody tests)
Were the index test results interpreted without knowledge of the results of the reference standard?	No
If a threshold was used, was it pre‐specified?	Yes
Could the conduct or interpretation of the index test have introduced bias?		High risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Yes
The reference standard does not incorporate the index test	Yes
Could the reference standard, its conduct, or its interpretation have introduced bias?		Low risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			High
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Unclear
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	No
Did all participants receive a reference standard?	Yes
Were results presented per patient?	Yes
Could the patient flow have introduced bias?		High risk