By; Theophilus Pius (MLA, MLT, BMLS, MPH, PGDME, PhD Fellow KIU) & Consultant Medical Laboratory Practitioner

Accurate laboratory diagnosis begins with proper sample collection. Often described as the ‘unseen iceberg’ of laboratory medicine, sample collection is a critical but less visible step that determines the reliability of laboratory results.

While sophisticated laboratory equipment and experienced personnel are important, even the finest laboratory cannot produce accurate results from a poorly collected, contaminated, or improperly transported specimen. Consequently, correct sample collection forms the base of quality laboratory diagnosis.

The pre-analytical phase which we currently refer to as pre-examination phase, includes patient preparation, specimen collection, labelling, storage, and transportation, accounts for the majority of laboratory errors. An error at any of this stage may lead to false results, delayed diagnosis, inappropriate treatment, or repeated testing.

For this reason, healthcare workers must follow Standard Operating Procedures (SOPs) during specimen collection.

Patient identification is the first and most important step. Before collecting any specimen, the healthcare provider should confirm the patient’s identity using at least two identifiers, such as the patient’s full name and date of birth or hospital identification number. Proper labelling immediately after collection helps prevent specimen mix-ups.

Different laboratory tests require different types of specimens. The correct specimen must be collected in the appropriate container and in sufficient quantity.

• Blood sample for a full blood count (FBC/CBC), venous blood is collected into a lavender top vacutainer containing EDTA. Using the wrong vacutainer, such as a plain vacutainer, may produce inaccurate results because the blood will get clotted.
• Urine sample for diagnosing a urinary tract infection (UTI), a clean-catch midstream urine specimen is collected in a sterile container to minimize contamination from skin bacteria (normal flora).
• Sputum sample for diagnosing tuberculosis (TB) requires an early morning deep cough sputum sample because, it contains a higher concentration of bacteria than saliva.
• Stool sample for identifying intestinal parasites requires a fresh stool specimen to be collected in a clean, dry container without contamination from urine or water.
• Wound swab for culture, the wound should be cleaned with 70% alcohol to remove surface contaminants so that the sample represents the actual infecting organism.

Proper handling and transportation are equally very essential. Some specimens require refrigeration, while others must reach the laboratory immediately. For example, blood cultures should be transported promptly to preserve bacterial viability, whereas cerebrospinal fluid (CSF) should never be refrigerated because this may reduce the recovery of certain pathogens.

Infection prevention measures must be followed during specimen collection

Healthcare workers should perform hand hygiene, wear appropriate personal protective equipment (PPE), use sterile equipment where necessary, and safely dispose of sharp needles and other waste to protect both patients and staff.

In conclusion, sample collection is the ‘unseen iceberg’ that strengthens the quality of laboratory diagnosis. Although it occurs before laboratory analysis, it has a major influence on the accuracy, reliability, and clinical usefulness of test results.

Right patient identification, proper patient preparation, correct specimen selection, appropriate collection techniques, accurate labelling, and timely transportation all contribute to high-quality and reliable laboratory services.

By abiding to an established SOPs, healthcare professionals ensure that laboratory results support accurate diagnosis, effective treatment, and improved patient outcomes. It is mandatory that all healthcare professionals are aware with procedures leading to quality and reliable laboratory diagnosis at the pre-examination phase as 46-70% errors occurred at this phase.