Blood samples are the preferred method for genetic analysis because they consistently provide a high quality and large yield of genomic material. This robust source of DNA is well-suited for complex genetic testing, such as whole-genome sequencing, which requires a substantial amount of intact DNA. Blood collection is the standard choice in many clinical settings, including diagnostics for genetic diseases, non-invasive prenatal screening, and establishing legal paternity. Blood remains a reliable option for tests where the comprehensive nature of the DNA profile is paramount.
Preparation Before Sample Collection
Proper preparation is necessary to ensure the integrity of the collected sample and prevent the need for a costly repeat procedure. The first step involves carefully reading all instructions provided with the testing kit or by the laboratory, as requirements can vary significantly. Some advanced genetic tests may require a period of fasting, typically 9 to 12 hours, to prevent dietary changes from temporarily altering blood components that could interfere with the analysis.
Timing the collection may also be important, especially if the test is looking for time-sensitive biomarkers or if the sample needs to arrive at the laboratory within a strict window. Before the physical collection, all required paperwork, such as consent forms and identification verification documents, should be completed. On the day of collection, strict hygiene must be observed, including washing hands thoroughly and preparing the collection site with an antiseptic wipe to minimize the risk of bacterial contamination.
Staying well-hydrated makes veins easier to access for a professional draw by increasing the fluid volume in the bloodstream. Conversely, activities like strenuous exercise, chewing gum, or smoking should be avoided immediately beforehand, as they can affect certain test results.
Methods of Blood Collection
The two primary methods for collecting a blood sample for DNA testing are clinical venipuncture and capillary blood collection. Venipuncture is performed by a trained professional, typically a phlebotomist drawing blood from a vein in the antecubital fossa, the inner crease of the elbow. This method uses a sterile needle and a vacuum-sealed tube, often containing an anticoagulant like EDTA, to collect several milliliters of whole blood, providing the highest possible DNA yield.
For at-home or less invasive collection, capillary blood is obtained using a fingerstick method, requiring only a few drops of blood. To prepare for self-collection, the individual should warm their hands to increase blood flow, perhaps by running them under warm water or rubbing them together. The ring or middle finger is usually the preferred site, and the fingertip must be cleaned thoroughly with the provided alcohol wipe and allowed to air-dry completely.
The process involves using a single-use safety lancet to quickly prick the side of the chosen fingertip, which is less painful than pricking the center. The first drop of blood should be wiped away, as it can be contaminated with tissue fluid, potentially diluting the sample. Subsequent drops are collected onto the designated material, often a Dried Blood Spot (DBS) card or a specialized microsampling device. Gentle pressure may be applied to encourage blood flow, but the finger should not be “milked” or squeezed too vigorously, which can damage red blood cells and compromise the sample’s quality.
Post-Collection Processing and Transport
After collection, immediate and correct processing is necessary to preserve DNA integrity before laboratory analysis. For venous blood collected in a tube, the container must be gently inverted several times (typically eight to ten) to ensure the anticoagulant thoroughly mixes and prevents clotting. Capillary samples collected on DBS cards require the spots to air-dry completely, a process that can take several hours depending on environmental conditions, before they are sealed.
Correct labeling is a non-negotiable step. The sample container must be clearly marked with the patient’s full name, date of birth, and the date and time of collection, ensuring all identifying information matches the accompanying documentation. Used lancets, wipes, and other contaminated materials must be disposed of properly in a designated biohazard bag or container, often provided in the kit, to protect others from potential contamination.
Transport Requirements
The stability of the DNA sample dictates the transport requirements, which must be followed precisely to avoid degradation and sample rejection. Whole blood samples are generally stable for up to 48 hours at room temperature, but refrigeration at 2 to 8 degrees Celsius is recommended if shipping is delayed beyond one day. Freezing must be avoided unless specifically instructed by the lab.
The packaged sample, including the required forms, must be placed inside the provided biohazard bag and then secured within the shipping box. This package is often sent with a cool pack and shipped via overnight priority mail. Failure to follow these transport instructions is a common reason for a laboratory to reject the specimen, requiring the entire collection process to be repeated.