Figure 3. The subgroup analysis results of association between the serum leptin levels and lung cancer in high-study quality group (NOS score≥7).

Failure of this confidence interval to include zero indicates no statistical difference between the case group and control group. Negative SMD value suggests the mean of serum leptin concentration of patients in high-study quality group is lower than that of control group, while positive SMD value suggest the mean of case group was higher than control group.