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. Author manuscript; available in PMC: 2022 Jan 1.
Published in final edited form as: Expert Rev Precis Med Drug Dev. 2021;6(1):1–4. doi: 10.1080/23808993.2021.1854611

Table 1.

Types of protein-directed diagnostic approaches and their dependence on an antigen-antibody interaction

In liquids (whole blood, serum, plasma, etc.) In tissues Dependence on availability of specific antibodies Features

  • Enzymatic activity assays (ALT, GGT, etc.)

  • Enzymatic activity assays (AChE, etc.)

 No

  • Indirect detection of enzyme by substrate transformation

  • Nephelometry

  • Flow cytometry

  • ELISA

  • Chromogenic immunohistochemistry

  • Immunofluorescence

  • Western blot

  • Ion beam imaging

 Yes

  • Quantitative but limited linearity

  • Affected by posttranslational modifications of epitopes

  • Antibody crowding limits multiplex depth

  • Mass spectrometry (LC-MS)

  • Mass spectrometry (LC-MS, MALDI-MS imaging)

 No

  • Detects proteins and posttranslational modifications for which no antibodies are available

  • Fully quantitative (relative and absolute)

  • Discovers posttranslational modifications (phosphorylation, glycosylation, acetylation, etc.)

  • Extreme multiplex detection depth

ALT, alanine transaminase; GGT, gamma-glutamyltransferase; AChE, acetylcolinesterase; LC-MS, liquid chromatography-mass spectrometry; MALDI-MS, matrix-assisted laser desorption/ionisation-mass spectrometry