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If along with ESR CRP or C-reactive protein is also high, then a Montoux test should be done to rule out tuberculosis. Some increase in ESR is expected in all fevers. Hence repeat the test after a week, preferably empty stomach. If it is still high, then chronic inflammatory diseases like Crohn's, rheumatoid arthritis, and conditions like tuberculosis will need be ruled out.
Please consult your PCP for primary examination followed by proper referral.