Background: Using a risk-based approach to QC requires estimating the risk of patient harm from erroneous results (in this case using a Risk Management Index‑RMI), after which, a lab must determine what to do if there is an unacceptable level of risk (RMI>1)?
To correct the situation, one must assess the components of risk. What part of the overall risk can be attributed to in-control imprecision, in‑control bias, or out‑of‑control conditions? If too many erroneous results are produced because of in‑control imprecision, there is no QC strategy that will fix it. A similar argument can be made for bias. While the production of erroneous results from out‑of‑control conditions is not independent of in‑control performance, it is still useful to assess how much risk is attributed to out‑of‑control conditions which may be mitigated by adjusting the QC strategy. The method below evaluates these risk components.
Methods: The sources of risk of patient harm from erroneous results are computed as:
PE(0)[probability of in-control erroneous results]=f(x)[1-Ф([x+TEa(x)-bias(x)]/ơ(x))+Ф([x-TEa(x)-bias(x)]/ơ(x))]
PEi(0)[probability of erroneous results from imprecision]=PE(0)-f(x)[1-Ф([x+TEa(x)]/ơ(x))+Ф([x-TEa(x)]/ơ(x))]
PEb(0)[probability of erroneous results from bias]=PE(0)-PEi(0)
PΔE[probability of out‑of‑control erroneous results] =∫[E(Nuf(SE))/[MPBF+ANPed(SE)] dSE over ±2 TEa range.
PE[probability of erroneous result]=PEi(0)+PEb(0)+PΔE
PPH[predicted probability of harm]=PE*Ph|u
Acceptable PH[acceptable probability of harm]is derived from Severity of Harm and risk acceptability matrix.
RMI (RMI<=1 indicates managed risk)=PPH/Acceptable PH
Formulas, terms and definitions are abbreviated for abstract.
Results: Computation Example
QC Strategy:2QC levels,1:3 Rule, every 50 results.
Conclusion: Breaking the RMI of a test method into the individual components of risk gives the laboratorian critical information for resolving risk issues – is the problem imprecision, bias or the quality control strategy, or some combination? Once the risk components have been evaluated, steps can be taken to mitigate risk by reducing the risk associated with bias, or imprecision, or the quality control strategy.