It is a foundational principle for any laboratory test procedure that the value of the test is compromised or even negated by using specimens that have not been properly collected, labelled, handled or stored prior to and during the testing process.
Microbiological tests are not as standardized as some other lab tests; the way in which a sample is processed and the results are interpreted depends heavily on the information provided with the specimen. Erroneous results as a result of specimen mis-management can affect patient care and outcomes, as well as hospital infection control, patients’ length of stay in the hospital, costs and laboratory efficiency.
The initial collection of samples for microbiology testing is critical, since errors that occur at this stage cannot be corrected at a later time, and since mistakes require collection of new specimens.
- Document that proper patient preparation prior to collection of the specimen has been done.
- A laboratory request form with the following information must accompany the specimen. This aids interpretation of results and reduces the risk of errors.
- Patient’s name, DOB, hospital number, and ward/department.
- Type of specimen and the site from which it was obtained.
- Date and time collected.
- Diagnosis with history and reasons for request such as returning from abroad (specify country) with diarrhea and vomiting, rash, pyrexia, catheters in situ or invasive devices used, or surgical details regarding post-operative wound infection.
- Any antimicrobial drug(s) given.
- Name and number of the clinician who ordered the investigation, as it may be necessary to telephone preliminary results and discuss treatment before the final result is authorized.
- Hands should be washed before and after specimen collection. In line with standard precautions, appropriate personal protective equipment should be worn when collecting or handling specimens.
- Specimens should be collected in sterile containers with close fitting lids to avoid contamination and spillage. It is not necessary to collect stool specimens in a sterile container. All specimen containers must be transported in a double-sided, self-sealing polythene bag with one compartment containing the laboratory request form and the other the specimen.
- Ideally microbiological specimens should be collected before beginning any treatment such as antibiotics or using antiseptics. However, treatment must not be delayed in serious sepsis.
- Transport medium may be used to preserve micro-organisms during transportation.
Tenets of Specimen Management
It is important to be knowledgeable of caveats that are relevant to specific specimens and diagnostic protocols for infectious disease diagnosis. However, there are some strategic tenets of specimen management and testing in microbiology that stand as community standards of care and that set microbiology apart from other laboratory departments such as chemistry or hematology. Ten points of importance are:
- The laboratory should set technical policy; this is not the purview of the medical staff. Good communication and mutual respect will lead to collaborative policies.
- The laboratory must follow its procedure manual.
- A specimen should be collected prior to administration of antibiotics. Once antibiotics have been started, the microflora change, leading to potentially misleading culture results.
- Specimens must be labeled accurately and completely so that interpretation of results will be reliable. Labels such as “eye” and “wound” are not helpful to the interpretation of results without more specific site and clinical information (eg, dog bite wound right forefinger).
- Microbiology specimens should be delivered to the testing laboratory without delay, and according to the lab’s requirements for specimen transport and stability.
- “Background noise” must be avoided where possible. Many body sites have normal flora that can easily contaminate the specimen. Therefore, specimens from sites such as lower respiratory tract (sputum), nasal sinuses, superficial wounds, fistulae, and others require care in collection.
- The laboratory requires a specimen, not a swab of a specimen. Actual tissue, aspirates, and fluids are always specimens of choice, especially from surgery. A swab is not the specimen of choice for many specimens because swabs pick up extraneous microbes, hold extremely small volumes of the specimen (0.05 mL), make it difficult to get bacteria or fungi away from the swab fibers and onto media, and the inoculum from the swab is often not uniform across several different agar plates. Swabs are expected from nasopharyngeal and viral respiratory infections
- Specimens of poor quality must be rejected. Microbiologists act correctly and responsibly when they call physicians to clarify and resolve problems with specimen submissions.
- Physicians should not demand that the laboratory report “everything that grows,” thus providing irrelevant information that could result in inaccurate diagnosis and inappropriate therapy.
- Susceptibility testing should be performed on clinically significant isolates, not on all microorganisms recovered in culture.
- Microbiology laboratory results that are reported should be accurate, significant, and clinically relevant.
The microbiology laboratory policy manual should be available at all times for all medical staff to review or consult. It would be particularly helpful to encourage the nursing staff to review the specimen collection and management portion of the manual. This can facilitate collaboration between the laboratory, with the microbiology expertise, and the specimen collection personnel, who may know little about microbiology or what the laboratory needs in order to establish or confirm a diagnosis.
Most infectious disease protocols have based their strategies on the management of results generated by microbiology laboratories. Getting the right diagnosis is contingent upon laboratory results that are accurate and clinically relevant.