Abstract
BackgroundInternal quality control (IQC) in clinical laboratories is carried out to monitor analytical stability. Usually, the satisfactory results of the IQC ensure the acceptability of the examination results. Here, we reported that patients' creatinine results are unreliable, although the internal quality control is satisfactory.MethodsCreatinine levels were analyzed from two quality control materials and twenty patients' specimens using two different lots of reagents. Lot‐to‐lot comparison was performed. The daily median values of serum creatinine levels of patients were calculated from the test results recorded in our laboratory information system.ResultsAlthough IQC was consistent, serum creatinine concentrations were higher using lot B (median: 153 μmol/L; interquartile range: 122‐522 μmol/L) than using lot A (median: 133 μmol/L; interquartile range: 76‐508 μmol/L) for 20 patients (P = .001). The Deming linear regression showed a best fit of y = 0.9394 × x + 45.66. R 2 = .8919, and mean percentage difference between two lots was 34%. The new lot was considered unacceptable. Likewise, the median serum creatinine level from the 360 patients using lot B was 102 μmol/L, which was significantly higher than the daily medians of patients using lot A (median: 66 μmol/L; range: 61‐70 μmol/L) in the previous month.ConclusionThe variations in creatinine concentrations proved to be due to different lots of reagents. However, IQC materials tested using both lots of reagent exhibited minimal variation. Therefore, IQC alone is insufficient for assessing laboratory analytical results. This finding prompts us to be vigilant in potential pitfall of interpreting test results based on satisfactory IQC alone.
Highlights
Laboratory medicine plays an important role in clinical diagnosis, treatment, and monitoring
The accuracy of laboratory tests is usually monitored through external quality assessment (EQA) (2‐3 times per year), while reproducibility of test results is commonly monitored through Internal quality control (IQC)
Our findings indicate that satisfactory IQC does not neces‐ sarily mean reliable analytical results in clinical laboratories
Summary
Laboratory medicine plays an important role in clinical diagnosis, treatment, and monitoring. Laboratory test results influence med‐ ical decision‐making in two‐thirds to three‐quarters of cases.[1] The goal of all clinical laboratorians is to provide high‐quality reported results in order to secure correct diagnosis, prediction, and deci‐ sion‐making during treatment and follow‐up.[2,3,4] The quality of re‐ sults usually includes accuracy and reproducibility. The accuracy of laboratory tests is usually monitored through EQA (2‐3 times per year), while reproducibility of test results is commonly monitored through IQC. We report an incident in which a batch of creatinine test results was found to be unreliable due to a change in reagent lots, even though IQC results were satisfactory
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