By W. Gregory Cooper, CLS, MHA
Laboratories typically require that quality control material encompass multiple analytes and have a long shelf-life.
In addition to the valuable information gained from the long-term use of a QC lot, there are financial advantages as well; long-term use saves costs and reduces the need for time-intensive QC lot crossover studies. However, oddly enough, sometimes when a new lot of a control is available, the money saving advantages of a long shelf life and avoidance
of crossover studies is overlooked. In recent years, Bio-Rad has noticed some laboratories abandoning the value associated with staying with an existing QC lot through its entire shelf life, and switching to a new lot once it becomes available. When laboratories do this, they incur unnecessary charges that they didn’t plan for in their current budget.
This brief article reviews costs associated with a cross-over study and the savings that may be obtained by appropriately timing a crossover study near the end of the useful life of the lot.
The costs associated with a QC material crossover study can be broken into variable costs and fixed costs. The variable costs of running the study include QC materials, reagents and consumables, along with the labor cost of staff running the tests and supervisors reviewing the data. Fixed costs include instruments, utilities, support staff, refrigerators and freezers used to store the control materials, and in some situations—the amortized cost
of laboratory space. For the purposes of this article, the fixed costs will be assumed to be negligible compared
to the variable costs. Similarly, QC material costs are relatively small compared to the costs of reagents and labor and are therefore, ignored.
To illustrate the costs, Bio-Rad’s QC product–Liquichek™ Cardiac Markers Plus Control LT will be used. It has three levels and ten analytes: BNP, CK (Total), CK-MB, CRP (hs), Digitoxin, Homocysteine, Myoglobin, NT pro-BNP, Troponin I, and Troponin T. A typical crossover study
is performed by obtaining one verified value for each level of the control for twenty days for a total of 20 data points per level or 60 data points in total.
The first example is a rudimentary cost analysis calculating total costs to run the crossover study with publicly available pricing on a cost-per-reportable basis and nationally published average labor rates. Actual costs will vary depending on contracted pricing with the lab and labor rates across the country. QC material costs are ignored for the purposes of this calculation due to the relative low cost compared to the reagents.
It is also assumed that each day of study, the technologist spends one hour preparing the materials, running the samples, verifying the information, documenting the results, and returning everything back to storage or waste. The supervisor is assumed to spend a total of two hours during the course of the study advising and reviewing data. A national average labor rate of $21/hour for
a technologists and $32/hour for a supervisor,
with a conservative markup for benefits of 35%,
brings labor rates to $28 and $43, respectively.
In the above example, the calculations for all analytes are used. In reality, some of the analytes are competitive and would not be run on the same instruments, such as BNP and NT-pro-BNP. A second analysis of the same QC material looks at costs associated with a laboratory running only 6 of the 10 analytes and the cost is still significant. In the following scenario, a smaller lab’s higher pricing is taken into consideration.
When assessing whether it makes sense to change lots early, laboratories must acknowledge that a QC lot change needs
to occur, and take into consideration the costs of the study. This would seem to indicate a cost deferment, not a cost savings. However, when assessed over a fixed period of time (5 or 10 years), the cost savings for a lab is quickly understood.
At the more conservative study savings of $2921, the laboratory only performs two crossover studies instead
of three—over a five-year period.
$2921, while notable, is the cost for only one control product on one instrument using 6 reagents. The costs rise significantly for instruments with dozens of reagents, or labs with multiple instruments switching QC lots
at the same time. Consider all the different QC products
a laboratory uses, and entertain the idea of the lab not ensuring the full utilization of a QC lot to the end of its useful life. The lab is likely to be running multiple QC studies every year well before they are necessary. In this scenario, the cost per year for premature cross-over studies across multiple products could easily exceed $10,000 in reagent costs alone.
Cost-conscious laboratorians know that in this era of budget tightening, any potential savings that do not affect quality should be taken. Committing to the same lot of QC material can free up thousands of dollars that could be available
for other resources.
To learn more about Bio-Rad’s Quality Controls, visit http://www.qcnet.com/independentQC/index.html