Appendix 1
APPENDIX: MODIFIED QUALITY ASSESSMENT OF DIAGNOSTIC ACCURACY STUDIES CHECKLIST
Domain 1. Patient selection
Risk of Bias: Could the Selection of Patients Have Introduced Bias?
Was a consecutive or random sample of patients enrolled?
We scored “yes” if patients were enrolled consecutively or randomly, or if Authors stated that all patients were included between a defined time period.
Was a case control design avoided?
We scored “yes” if a case-control design was avoided.
Did the study avoid inappropriate exclusions?
We scored “yes” if studies do not exclude subjects with clinical picture suggestive of NEC at any stage.
Applicability concerns: Are There Concerns That the Included Patients and Setting Do Not Match the Review Question?
We scored “low” this item if the study included preterm neonates with signs and symptoms suggestive of NEC or with risk factors for NEC, that do not had received diagnosis of NEC Bell stage ≥ 2 at the enrollment.
We scored “high” if at term neonates, or preterm neonates with definite or surgical NEC were included at the time of enrollment.
We classified as “unclear” this item if insufficient data on presenting symptoms were reported.
Domain 2. Index test
Risk of Bias: Could the Conduct or Interpretation of the Index Test Have Introduced Bias?
Were the index test results interpreted without knowledge of the results of the reference standard?
We scored “yes” if the index test results were interpreted without knowledge of the reference standard.
We scored “no” or “unclear” if the interpreters of the results of the index test were not blinded to the reference standard results or if the use of blinding methods was not explicitly reported, respectively.
If a threshold was used, was it pre-specified?
We scored “yes” if the threshold was pre-specified and defined in previously studies including preterm neonates, or if a cut- off value was defined by using adequate statistical methods.
We scored “no” if the threshold was defined arbitrary (i.e., by using cut-off indicated by manufacturer), or previously defined in population different from our setting.
We classified “unclear” this item when the above mentioned aspects were not clearly explained.
Applicability concerns: Are There Concerns That the Index Test, Its Conduct, or Its Interpretation Differ From the Review Question?
We scored “low” if the study provided a clear description of the index test, laboratory technique, and definition of a positive test result.
We classified as “unclear” this item when the index test, its conduct and interpretation were not clearly described.
Domain 3. Reference Standard
Risk of Bias: Could the Reference Standard, Its Conduct, or Its Interpretation Have Introduced Bias?
Is the reference standard likely to correctly classify the target condition?
Despite limits the Bell’s criteria remain the gold standard for the diagnosis of NEC. We scored “yes” if the reference standard was Bell’s staging, modified Bell’s staging, or histopathology for surgical NEC.
Were the reference standard results interpreted without knowledge of the results of the index test?
We scored “yes” if the reference standard results were interpreted without knowledge of the index test.
We scored “no” or “unclear” if the interpreters of the results of the reference standard were not blinded to the index test results or if the use of blinding methods was not explicitly reported, respectively.
Applicability concerns: Are There Concerns That the Target Condition as Defined by the Reference Standard Does Not Match the Question?
We scored “low” if the target condition was NEC Bell stage ≥ 2.
We judged “high” the concerns on this item, if also other diseases (i.e. sepsis, bacterial infection, intestinal inflammatory conditions) or NEC Bell stage < 2 were considered as “target condition”.
Domain 4. Flow and Timing
Risk of Bias: Could the Patient Flow Have Introduced Bias?
Was there an appropriate interval between index test and reference standard?
We scored “yes” if the blood samples were collected at symptom onset and before the diagnosis of definite NEC based on (modified) Bell’s criteria.
We scored “no” if blood samples were collected after diagnosis of definite or surgical NEC.
We judged this item as “unclear” if the Authors did not clearly explain the timing of sample collection.
Did all patients receive a reference standard?
We scored “yes” if all patients received a reference standard.
Did all patients receive the same reference standard?
We scored “yes” if all patients received the same reference standard.
Were all patients included in the analysis?
We scored “yes” if all patients included in the study were included in the analysis, or number of patients lost to follow-up and reason for withdrawal were clearly specified.
We scored “no” if the number of patients included in the analysis differed from the number of patients enrolled without justification.
We judged “unclear” this item if the number and cause of subjects lost to follow-up were not clearly reported.
Note: if all answers to signaling questions concerning a domain were “yes”, the risk of bias was judged as low. If at least one signaling question was answered “no”, the risk of bias was judged as “high”. If answers to the signaling question concerning a domain were “yes” and/or “unclear”, the risk of bias was judged as “low” or “unclear” after discussion and attainment of consensus between the reviewers.
Competing Interest
All the authors have no conflicts of interest to disclose.
Authors’ contributions to manuscript
GT, LS, SC and MDC conceptualized and designed the study; GT and LS screened data source and selected studies; GT and LS extracted data; GT and MDC assessed study quality. GT, LS wrote the first draft of the manuscript. SC and MDC critically reviewed and revised the manuscript. All the authors read and approved the final version of the manuscript.
