In a previos post : “When the QC’s out of range” we went over what to do when the quality control runs out of their acceptable ranges, but how, where and when are these controls used in the laboratories? And what is a Core Lab? In this blog post we would be discussing what is a core lab, where are they generally situated and how is the quality control implemented in the core labs?
As a medical laboratory scientist, the first job I landed after graduation was in a core lab. Core labs are smaller versions of medical laboratories. These labs are generally situated in small towns or rural areas, attached to a hospital. These labs provides urgent care service to the hospital and conducts testing on the most requested community tests. All the other tests are sent to other specialised and referral labs, following the appropriate procedures and maintaining proper transportation conditions. These labs generally have 3-4 departments being handled by a small number of staff who are competent at working in all departments of the lab.
Read more about the core labs at: workflow in a core lab
Types of QC in core medical laboratory
Lets now talk about the quality controls in core labs. The core labs have 3-4 major departments: mainly biochemistry, haematology, transfusion science and microbiology. Along with the early morning lab tasks and maintenances, the other important task performed in the lab is to run QCs across all these departments. For the analysers and tests that are used more frequently like the Heam and chem analysers the QCs are run daily while weekly for departments with low sample volumes.
QC in Biochemistry department
Start of the day maintenance in the chemistry department is generally followed by running quality controls on all the analysers in use. This is a routine practice that is important to rule out any errors in the functioning of the analysers.
In chemistry the QCs can be further classified into: daily, weekly, monthly and yearly QC based on how often they are performed. The daily QC is run at the start of the day and at specific intervals set by the labs based on the stability of the assays. A monthly review on the trend of the QC is carried out by the section leader or lab manager (in smaller labs).
The weekly QC generally includes performing the interanalyser QCs and comparing the results produced by their analysers. Along with that, labs generally keep a check on the hemolysis (H index) and icteric (I index) in the weekly QC process.
Most labs are generally involved in external quality assurance programs. These labs receive external QC material from the program coordinator. These QCs are performed as and when the sample is received by the labs or as scheduled. The chemistry department of most labs in NZ are enrolled in RCPA EQAs .
All the documents and records of these controls are maintained and are inspected during the IANZ audits.
QC of Point of care devices
For urgent tests, most labs use the point of care devices in rural areas. They are also used for testing short aged samples like blood gases, troponin and other tests like chem8. QCs are run on the POC devices by running a stimulator. If the stimulator passes, the samples can be run on the device.
The monthly QCs involve keeping an eye on the expiry date of when the last QC was performed and running the controls on new cartridges and the stored cartridges before they come into use. This is an important step as the cartridges are temperature sensitive and the temperature needs to be monitored closely when being transported.
The external QCs for the point of care devices are provided to the labs in bulk and are performed as scheduled by the labs. Most New Zealand labs use RCPA controls for point of care testing and the results are submitted on the RCPA submission portal. External stimulators are also received once or twice an year to make sure that the POCT analysers are functioning properly.
QC in Haematology department
Haematology analyser (complete blood count)
Similar to the chemistry analysers, the morning QCs are run on the cbc analysers and coagulation analysers. The CBC analysers use 3 levels of the controls, these generally consist of abnormally low, normal and abnormally high level of control. This is done to check that the machine can accurately measure the normal as well as abnormal results accurately. These QC results are displayed in the form of graphs and LJ charts, which are analysed by the medical technicians and scientists. The controls that are out of range are recorded and troubleshooted. These QCs like the chemistry controls are reviewed and changes in the QC ranges are made as needed. Most of the analysers have an online database that accumulates and compiles all the QC data that is reviewed frequently and used to troubleshoot out of range QC. Eg careshpere software used by sysmex.
Erythrocytic sedimentation rate
Most of the core labs use the manual method of performing ESR testing. The ESR controls have 2 levels with a range that is worked out by the labs that make up and supply these controls to smaller labs (core labs). They generally include one normal and abnormal level of the control. The ESR controls are run once a day alongside the first sample received and the results are recorded on the spreadsheets dedicated to storing the ESR control information. These QC records are also used for reviewing how well the QC is performing and also for inter-laboratory analysis.
Coagulation analysers
Apart form the start of day QC the coagulation QCs are run every 6-8 hrs depending on the stability of the reagents. Some labs choose to run QC for all the tests performed on the analysers while other labs choose to perform the QCs when they receive a sample for the required tests.
For ex. some labs may run the qc for all the tests included in the coagulation screen like Prothrombin ratio (PR), Activated Partial Thrombin time (APTT) , Fibrinogen (Fib) and Thrombin Clotting Time (TCT), while other might choose to run QC on the most frequently run sample like the PR and run other controls as they receive the sample for the requested tests like APTT, Fib etc. This is totally dependant on the number of samples received by the lab for a certain test. Coagulation screen external QCs are recieved by the labs weekly or monthly depending on the program that the lab choose to participate in.
Slide stainers
The qc slides are prepared to check the quality of the stain used in the haematology department any time the reagents are changed or after alteration in the stain settings. It may also be performed after performing monthly maintenance on the staining machine.
The Haematology departments of the labs in nz generally participate in both the Waikato and RCPA QAP for both the CBC and coagulation sections. Waikato samples are freshly collected blood in EDTA tubes and are dispatched to the labs enrolled in the program. These fresh blood samples along with the blood films are received by the labs on fortnightly basis. The blood films are intended to be completed by every individual working in the Haematology department or is intended to have minimum 70% engagement annually. CBC is run on the analyser and the result are recorded online to the Waikato or RCPA site where they are complied and available for labs to review and for inter lab comparisons. Some labs also perform inter-analyser QC to standardise the results produced by the diff analysers. These inter-analyser testing are carried out weekly.
QC in Transfusion department
Most of the core labs generally have a combination of Haematology, chemistry and blood bank and/or microbiology departments or one of two. The blood banks are important to issue emergency transfusion units to the hospitals and other blood and blood related products to the patients. The QC materials are centrifuged at the start of the week and new cell suspensions are made from the QC material in blood bank. Blood bank in a core lab generally has three types of grouping controls, which have a predefined blood groups (example blood group A and B controls and Coombs positive controls).
The controls of the blood bank may be changed/ replaced every week or on expiry and hence the QC is performed on them weekly and recorded on the QC signing off sheets or spreadsheets. These controls are also run along side the actual sample to assure that the samples have been processed accurately, following the correct procedure. The QCs are also run on the blood bank testing cards when a new delivery is received. This is done to validate the blood bank cards and bring them into day to day use.
QC in Microbiology department
In microbiology the QC plates and broths are prepared at the start of the week for the selected organism that the lab tests for. The QC plates are prepared from the previous culture plates using streak plating method. The growth on these culture plates are observed the next day to determine if the culture QC has passed.
The sensitivities are set up weekly on the selected organism using the lawn method and the antibiotics stamper is stamped onto the culture plate and kept in the incubator for 24 hrs. The diameter of the inhibition zones on these plates are measured and recorded on the dedicated spreadsheets. If the diameter of the zones are within the set range the QC have passed but if the zone is out of the set range, the QC have failed and need to be repeated and troubleshooted. New swabs are received each month and new culture plates are subbed monthly.
New delivered culture plates/ the plates with new lot number received monthly or as ordered and scheduled are QCed on arrival and stored appropriately. The disc sensitivity QC are also performed on the change of the antibiotics to a new lot to being it into used. Gram stain slides are made and the QC is signed off to make sure the stain is functioning properly.
Monthly QC is also performed on all the other reagent kits like the catalase, latex test, strep grouping etc that are used by the laboratory. These tests are performed and signed off from the monthly QC worksheets.
Conclusion
QC is an indispensable part of the laboratory testing. These quality controls help to rule out any errors that might effect the patient results generated by the laboratory and keep a check on and establish confidence on the services provided by the lab. These QCs are also implemented in all the departments of the core laboratories. These controls may be divided into daily, weekly, monthly and yearly, and which can be further classified into internal and external forms of QC and are performed in the laboratory as scheduled.