The best replacement for nitrites is nitrates.

The best alternatives to nitrites are rated as following:
★★★★★  nitrates
★  leukocytes
  sodium nitrates
  leukocyte esterase

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Speaking about nitrites, one probably shouldn't forget about leukocytes.

Other search terms related to nitrites and their ratings are:
★★★★★ leukocytes
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Google Trends

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nitrites
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leukocytes