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Table 2 Bias assessment framework of included articles

From: What is the effect on antibiotic resistant genes of chlorine disinfection in drinking water supply systems? A systematic review protocol

Bias area Characteristic Bias assessment Bias score
Selection and performance bias: study design Sampling Description of sampling method and transfer of samples to the laboratory 10
Description of the sampling method or transfer of samples to the laboratory 5
Method of sampling and transfer of samples to the laboratory is not described 0
Sample size Number of samples > 5 or sample size > 10 L 10
Number of samples < 5 or sample size < 10 L 5
Lack of sample size and number of samples 0
Replicates Replication of samples Yes [10]
   No [0]
Study timeframe Sampling time of more than two seasons (cold and hot seasons, winter and spring or summer) 10
  Sampling time of less than two seasons (hot or cold seasons) 5
  Sampling time is not described 0
Assessment bias: measurement of outcome Detection of ARGs The laboratory method and DNA extraction are clear [such as PCR, qPCR, HT-qPCR, high-throughput sequencing (HTS)] Metagenomics 10
  Laboratory methods and DNA extraction are unclear or not described 0
Chlorine measurement Using standard methods to measure chlorine (exposure) 10
  Using non-standard or unknown methods to measure chlorine (exposure) 0
Confounders Measuring confounding factors and their effects are applied (such as pH, temperature, DO, TOC, phosphate, and nitrate) 10
  Measuring confounding factors, but their effects are not applied 5
  Unmeasured confounders 0
Bias linked to clarity and publication bias Statistical analyses Using and describing the statistical data analysis method Yes [10]
   No [0]
Reporting bias All the statistical tests, measurements, and variables mentioned in methods are reported in the results or additional files Yes [10]
   No [0]
Other biases Detection bias Having significant differences in the results before and after chlorination Yes [10]
   No [0]
Attrition bias Measuring the concentration or frequency of ARGs before and after chlorination Yes [10]
   No [0]
Research aim consistency Objectives of the study are clearly stated and the answer is consistent with the objectives Yes [10]
   No [0]