Hiv i/ii combi - clia test after 6 months came as 0.21 non reactive and after 12 months value was 0.45 and non reactive. can any one tell me why there is raise in value. should i worry about this value change?

Such outcomes are entirely normal for this kind of test. The exact same specimen tested 10 times would give 10 different numbers. It has to do with the technology and biochemistry of the test. As long as the number is below the cut-off when the test is run, it is negative and there is no difference between say results of 0.10, 0.20, 0.40, or 0.80. All totally negative.