Sometimes inconclusive results are down to factors outside of anybody’s control, but there are a number of things that field samplers can be doing to mitigate that risk and lower the chance of getting unclear survey outcomes.
These are the 3 main things to consider for avoiding inconclusive test results
Contamination
Use equipment correctly
Change gloves with every sample. Use a new bag, ladle, or bottle for each sample. When sampling rivers, start downstream and work upstream, holding your vessel opening pointing upstream — and stand downstream of it to keep your own DNA out.
Decontaminate between sampling sites
Decontaminate equipment between sampling sites e.g. boots or waders with bleach between waterbodies. Contact NatureMetrics for advice on appropriate procedures.
Include field negative controls
Include at least one field blank per sampling day. Our lab processes it alongside your samples to check for in-field contamination. NatureMetrics provides one free blank kit when you purchase 20 or more aquatic eDNA kits.
Inhibitors
Inhibition occurs when compounds in the sample interfere with the PCR reaction, preventing or reducing DNA detection.
Key things to avoid:
Degradation
DNA degrades faster in heat, direct sunlight, and certain water conditions.
To minimise risk:
Detection masking
Large DNA volumes from abundant, mating and spawning species can mask rarer ones in broad tests. If you're surveying for a specific group, pair a broad test with a targeted test for the most complete picture.
Broad community screening across many taxa
qPCR (Targeted) — Use When:
Single-species confirmation (e.g. crayfish, eel)
Regulatory compliance requiring presence/absence
High-sensitivity detection of specific invasives or protected species