Thursday, June 20, 2019

by TERESA A. SCOTT, MT(ASCP)

According to the CLIA regulations, “laboratories eligible for a certificate of waiver must follow manufacturers' instructions for performing the test.”  This is also a requirement for non-waived testing.  Many people think that they are fulfilling this requirement if they follow the step-by-step procedure for the test process included in the instructions.  However, there is much more involved than just following the procedural steps.

Manufacturer’s instructions are found in instrument operator’s manuals and in package inserts; however, this article focuses on the instructions found in package inserts.  In addition to the procedural steps, the package inserts include information and instructions for 

• specimen collection and handling;
• reagent and test kit storage and expiration; 
• quality control;
• expected results and interpretation of these results;
• test limitations, precautions, and warnings; and 
• other pertinent information that affects the quality of test results.  

Inaccurate and unreliable test results may be obtained if the instructions are not followed.  Also be aware that   any modifications or changes may result in changing the test system from waived to high complexity.  Then, the certificate of waiver no longer applies, and all of the high complexity requirements (including Personnel eligibility requirements and responsibilities, Proficiency Testing, and Quality Assessment, etc.) will have to be met.

Package Insert

To follow the manufacturer’s instructions, you should understand every aspect of all package insert sections.  Depending on the manufacturer, the sections will have different titles, but all of the following information should be available in the package insert.  To be aware of all the information, it is imperative that you read the entire insert prior to performing patient testing.

Throughout the rest of this article, each section includes a description of what you can expect to see in the package insert and at least one example of how that information may be presented.

Test Procedure

The test system package insert will contain a step-by-step procedure of how to complete the test.  Depending on the manufacturer, specimen collection and other pre-analytic actions may be included.  

1. Read all instructions prior to performing patient testing.
2. Assemble all necessary materials.
3. Insert test strip into meter, with the sample collection area facing to the left, away from meter.
4. Apply a single drop of whole blood to the test strip “sample collection” area.
5. Compare the “test reaction” area to the meter’s color chart exactly 60 seconds after blood drop is applied.

Package inserts for reagents, cartridges, test strips, etc. may list only the steps that involve these products.  Some may not state any procedural steps, opting instead to refer the user to the test system package insert or the instrument manual.  

Specimen Collection and Handling

Tests may be designed for one type of specimen (e.g. whole blood) or several different types (e.g. whole blood, urine, throat swab, etc.).  The package insert will state this as well as how the specimen should be collected, handled, and stored.  Conditions that would cause specimens to be unsuitable for testing and any timing constraints will also be listed.  

This test is performed on whole blood, collected in an EDTA-anticoagulated tube (lavender top).  Following collection, specimens should be stored at room temperature for no longer than 8 hours.  If testing cannot be completed within 8 hours, refrigerate specimens at 2-8°C for up to 48 hours.  Clotted specimens should not be used for testing.

Reagents

Package inserts for test kits will list the reagents included in the kit.  They may also list other materials needed to perform the test, dividing them into two categories: materials supplied in the kit and materials needed but not provided.  Storage conditions, special handling requirements, and expiration dates for the test kits and the individual reagents will also be listed.

This package contains only reagent test strips.  A test strip reading meter, alcohol wipes, gauze pads, and skin-lancing devices will be needed to perform testing, but are not included in this package.  

Test strips must be stored in their original container, with the lid tightly closed, to protect them from moisture.  Store at 22-30°C and protect from humidity and temperatures beyond the stated range.  When proper storage conditions are maintained, the test strips are stable until the expiration date stamped on the container label. 

Quality Control

Pay special attention to this area of the package insert since it is the section that is most often overlooked.  Many testing devices have internal controls built-in as part of the test.  However, just as many require some sort of external quality control to be run at specific intervals: once each day, once each shift, with each new shipment, the first run of a new lot number, etc.  The package insert will list the type(s) of controls to test as well as when to test these controls.  Controls must be performed as required by the manufacturer.

Prior to reporting patient results, you must 

• Perform all required QC;
• Review QC results to ensure they are acceptable;
• Document that QC has been run, reviewed, and is acceptable.

Do NOT report patient results if QC results are not acceptable.  Instead, investigate the cause of the QC failure, perform the necessary corrective actions, re-run the controls, and document everything.  Do not report patient results until the problem is identified and corrected, and QC results are acceptable.  If the problem cannot be identified and/or corrected, perform testing by an alternate method, which may include sending the specimens to another laboratory for testing.

The ABC test system automatically runs a comprehensive set of quality checks of analyzer and cartridge performance each time a sample is tested.  This internal quality system will suppress results if the analyzer or cartridge does not meet certain internal specifications.  If the analyzer or cartridges have been compromised, results may be persistently suppressed and one or the other must be replaced to restore normal operating conditions.

Since storage and shipping conditions vary, external controls (normal, high, and low) must be run on each new cartridge shipment and each new cartridge lot number.

Expected Results and Interpretation of Results

Qualitative tests verify the presence or absence of the analyte.  Quantitative tests will produce numeric values that have to be compared to a reference range to determine if the result is normal or abnormal.  When applicable, the package insert will list reference ranges for different types of patients.  For example, the reference range for men may be different than that of women, or the range for adult patients may be different than that of pediatric patients.  If the test system has been approved for different types of specimens, expected values for each specimen type would be listed as well.

In some instances, the reported result is in a different format than the value obtained through testing; that is, the test result has to be interpreted before it is reported.  The information in these sections of the package insert will help you determine what to report and how to report it.

The XYZ test system is very sensitive to technique; thus each laboratory should establish its own normal range based upon its own techniques, controls, equipment, and patient population.  The sample can then be classified as negative, weak positive, or strong positive.  

The following can be used as a general guideline.

The interpretation could be nothing more than verifying that the test result falls within the instrument’s reportable range.  If it does not, the result would be reported as “less than” or “greater than” the range limit.  Since most instruments suppress or flag values for results that fall outside of this range, the interpretation is relatively simple.  

Tests that rely on color change can be more difficult to interpret, especially if it is left to the human eye to determine the amount of change.  The timing of the color comparison can also greatly affect result interpretation.  Some colors may diminish quickly after the reaction occurs, while others may be enhanced over time; either will cause inaccuracies in result interpretation.  In most cases, automated systems are available to simplify this interpretation.

Research studies performed to determine this data may be included as additional information in this section.

Test Limitations, Precautions, and Warnings

The information included here varies greatly and may include:  

• Hazardous reagent ingredients 
• Sodium Azide, used as a preservative, is a poison and may be toxic if ingested or absorbed through the skin.
• Safety precautions
• Always wear gloves when handling reagents.  If skin comes in contact with reagent, flush exposed area by holding under cold running water for 10 minutes.
• Substances that interfere with testing
• Reagent bubbles may interfere with proper detection of reagent level in the cartridge.  If present, remove air bubbles with a clean applicator stick.  To minimize volume depletion, do not use a transfer pipette to remove the bubbles.
• Patient conditions that may interfere with testing
• Patients receiving peritoneal dialysis using solutions that contain icodextrin should not use the KLM test system, since the dialysis solutions may falsely raise blood glucose results.
• Limitations on test performance
• Performance characteristics have not been established for specimens other than whole blood.  Reference ranges have not been established for neonates, infants younger than 2 years of age, or pregnant women.

This is by no means a comprehensive list and further serves to stress the importance of reading the entire package insert.

Other Pertinent Information

The information included in this area also varies.  What is considered “pertinent” depends upon what is in the package.  Test kits will have different information than control materials.  Reagents, test strips, and test cartridges will have different information than hand held meters.  Possible package insert section titles include:

• Intended use
• Explanation of the test
• Principles of the procedure
• Instrument calibration
• Performance characteristics (reference range, specificity and sensitivity, accuracy and precision)
• Method comparison
• Important information
• Technical information

As with the last section, this is by no means a comprehensive list.  Again, it only serves to stress the importance of reading the entire package insert.

Manufacturer’s instructions must be followed whether the test is waived or non-waived.  Waived tests, by definition, “employ methodologies that are so simple and accurate as to render the likelihood of erroneous results negligible.”  However, this is only true if all of the manufacturer’s instructions are followed.  

TERESA A. SCOTT, MT(ASCP)

COLA Education Division Medical Technologist