How DNA leaves the body and reaches the sequencer
Saliva, buccal swab, or venous blood — each route trades convenience for yield and stability in a different way. This hub explains the four common collection paths used in hereditary-cancer testing, with researched figures on yield and shelf life, and signposts the spoke pages for each method. Educational explainer only — not medical advice.
Why the collection step matters
Every downstream assay — multi-gene panel, targeted BRCA1/BRCA2 analysis, or whole-exome sequencing — inherits the quality of the sample it started from. The collection method sets three things before a pipette is ever lifted: how much DNA you recover (yield), how intact and contaminant-free it is (quality), and how long it survives in transit (stability).
There is no single "best" source. Venous blood gives the highest, cleanest yield but requires a phlebotomist and cold logistics; stabilised saliva in a kit such as the OG-500 returns ample DNA and ships at room temperature; buccal swabs are the simplest to self-collect but yield the least and most variably. The right choice depends on the study design, the participant population, and the shipping constraints — which is what the four spoke pages below unpack in detail.
Collection methods compared
Researched yield and stability figures for the common DNA collection routes. Yields vary widely with individual biology and extraction protocol — ranges are given where the literature reports them.
| Method | Sample / device | Typical DNA yield | Ambient stability | Notes |
|---|---|---|---|---|
| Stabilised saliva | 2 mL into OG-500 lysis buffer | ~110 µg median | Room temperature, months to years | Highest participant compliance; bacterial DNA fraction varies |
| Buccal swab | Cheek scrape, dry or buffered | ~0.2–60 µg (median ~54 µg), wide range | Days dry; longer if buffered/desiccated | Simplest self-collection; lowest, most variable yield and quality |
| Venous blood | 2–10 mL in K2EDTA (lavender-top) | ~30–40 µg per mL | Days at 4 °C; long-term at −80 °C | Highest, cleanest yield; needs phlebotomy + cold chain |
| Dried blood / buffer-preserved | Spot card or preservation buffer | Lower than liquid blood | Weeks at room temperature | Logistics-friendly archive format; see stability spoke |
Table 1. Comparison of DNA collection methods for germline (hereditary-cancer) testing. Figures are typical adult values from manufacturer technical specs and peer-reviewed comparison studies; individual results vary.
The four collection spokes
Each method has its own page with device codes, handling steps, and the trade-offs that matter for a hereditary-cancer workflow.
Saliva collection kits
How stabilising kits like the OG-500 capture ~110 µg of DNA from 2 mL of saliva and hold it at room temperature for months — and why bacterial content is the catch.
Buccal swabs
The simplest self-collection route, the most variable yield. What a cheek scrape actually recovers, why quality runs lower, and where swabs still make sense.
Read the swab pageBlood-draw vacutainers
Why K2EDTA lavender-top tubes are the reference standard for germline DNA, how EDTA protects the sample, and the ~30–40 µg/mL yield they deliver.
Sample stability & storage
From the moment of collection to the extraction bench: temperature, time windows, preservation buffers, and how each method's shelf life shapes your logistics.
Read the stability pageFrom swab to sequencer
The collection step is the first link in a chain. Here is where it sits in the broader workflow.
- 01
1 · Collect
Saliva, swab, or blood enters a stabilising device —
OG-500, a buffered swab, or aK2EDTAtube — that protects the DNA from the moment of sampling. - 02
2 · Stabilise & ship
Non-invasive kits travel at room temperature; blood often needs a cold chain. Stability dictates the shipping window — see the storage spoke.
- 03
3 · Extract
At the lab, genomic DNA is purified from cells. Higher, cleaner input yields more reliable libraries downstream.
- 04
4 · Sequence & interpret
The purified DNA feeds panel or exome sequencing; variants are classified against ACMG criteria. Quality set at step 1 echoes all the way here.
Collection — common questions
Does the collection method change the genetic result?
In principle, no — the germline DNA sequence is the same whether it comes from blood, saliva, or a cheek swab. In practice, a low-yield or degraded sample can fail QC or force a re-collection, so the method affects reliability and turnaround more than the final variant call. Labs set a minimum DNA input for each assay.
Why is saliva so popular if blood gives the cleanest DNA?
Compliance. Comparison studies report blood return rates around 31% versus 72% or more for saliva and swab kits, because participants can self-collect at home without a phlebotomist. For a registry chasing large enrolment, that difference in return rate often outweighs blood's yield advantage.
Is bacterial DNA in saliva a problem?
Saliva carries oral bacteria, so a fraction of the recovered DNA is microbial rather than human. Modern stabilising kits and extraction chemistries reduce this, and the human fraction is usually ample for panel testing. It is one reason quality-control metrics matter — discussed on the saliva spoke.
How long can a sample wait before extraction?
It depends entirely on the device. Stabilised saliva holds at room temperature for months; a K2EDTA blood tube is good for days at 4 °C and long-term only when frozen. The sample-stability spoke sets out the windows for each route.
“The result is only as trustworthy as the sample it began with. We treat collection as the first analytical step, not a clerical one.”
Read the explainer guides
Plain-language pieces on hereditary-cancer testing, sample handling, and reading a genetic report — written for the curious reader, reviewed for accuracy. For a personal testing decision, speak with a clinician or genetic counsellor.