What should be done for a 4-year-old girl with esr 55 in blood examination?

ESR: ESR (erythrocyte sedimentation rate), aka: "sed rate" is a non-specific marker of inflammation. By itself, the number does not determine next step in management. Would need to know the history/reason for the test, physical exam findings, as well as other blood tests done to give more definitive "next steps". Follow up with your pediatrician so they can review all tests and make appropriate recs.

It depends : in the reason the test was initially ordered. ESR is a very nonspecific marker for chronic inflammation. There are many potential causes of this. A general approach would be to perform further tests to determine the cause, and repeat ESR to evaluate the effectiveness of treatment.