It is much nicer to have an index that adapts itself to all changes but the adding/deleting/rearranging of \index commands.
Our package robustindex.sty (version 2017/09/28) achieves this with the \pageref mechanism.
Here is our Manual for the robustindex package.
Just try what happens if you put \usepackage{robustindex} in your preamble. Do read your TeX log file.
The sample file robustsample.tex illustrates more than you ever need. It also requires the package robustglossary.sty.
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If you want multiple indexes with pagerefs you may try \usepackage[multind]{robustindex}.
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