A Survey of Sigma Metrics across Three Academic Medical Centers.

BACKGROUND: Sigma metric calculations provide laboratories an objective means to assess analytical method performance. Methods with higher sigma values are desirable because they are more reliable and may use less frequent quality control in order to maintain optimal performance. Sigma metrics can also serve as a tool when comparing method performance across assay and manufacturer platforms. METHODS: Sigma values were calculated for 28 common chemistry and 24 immunoassay assays across 3 academic medical centers. Method imprecision and percent bias relative to peer group means was tabulated from Bio-Rad quality control (QC) data. Sigma values were calculated for each method using allowable total error (TEa) from either the CLIA evaluation limits or desirable biological variation. Average sigma values were generated for each site and graded as optimal: >6 sigma; good: 5-6 sigma; marginal: 3-5 sigma; or poor: <3 sigma. Analysis of NIST SRM1950 standards for a subset of analytes allowed an estimation of absolute bias. RESULTS: Clinical chemistry assays displayed similar method performance across all 3 study sites. Immunoassays showed significant differences between manufacturers, and a majority of assays failed to meet an optimal level of performance. Different TEa values produced different sigma metrics with more stringent TEa limits based on biological variation, resulting in poorer performance estimates than the wider CLIA limits. Analysis of NIST standards revealed similar performance. CONCLUSIONS: Sigma metrics are comparable for chemistry but not immunoassay platforms. The selection of total allowable error goals led to differences in sigma metrics.

Preanalytical Challenges During Capillary Fingerstick Sampling Preclude Its Widespread Use in Adult Hospitalized Patients.

OBJECTIVES: Patient compliance with laboratory testing is one of the most underrecognized challenges in developing a treatment plan for acute and chronically ill patients. The ability to offer alternatives to standard venipuncture blood draws would greatly increase a laboratory's ability to provide testing to patients and health care providers. METHODS: We performed a prospective observational study on paired venous and fingerstick capillary blood samples from admitted patients undergoing vancomycin therapy. Paired specimens were analyzed for vancomycin and a basic metabolic panel (BMP: calcium, carbon dioxide, chloride, potassium, sodium, creatinine, glucose, serum urea nitrogen) on the core laboratory's automated chemistry and immunochemistry platforms. RESULTS: A total of 59 paired fingerstick and venous blood specimens from 56 unique inpatients were analyzed. Paired samples were comparable for all the analytes tested with the exception of bicarbonate and potassium, which were significantly different among the capillary sample group. Patients required multiple fingers be lanced in 15% of cases to obtain sufficient blood to carry out the testing. Capillary sample rejection rates due to insufficient volumes were as high as 30% in the initial 30 patients enrolled in the study. CONCLUSIONS: Vancomycin and the BMP, with the exception of potassium and bicarbonate, were determined to be analytically comparable. However, significant preanalytical issues should preclude laboratories and providers from more widespread adoption of fingerstick-derived capillary blood as an alternative sampling method except in the most extenuating of circumstances.

Dilution of Urine Followed by Adulteration in an Attempt to Deceive the Laboratory.

Adulteration of samples submitted for toxicological analyses can present unique challenges to non-forensic clinical laboratories. With the number of overdose-related deaths expected to surpass 60,000 in 2018, it is incumbent on all members of the healthcare team to be active participants in curbing opioid dependence and identifying prescription drug misuse and diversion. Recently published guidelines have sought to provide guidance to laboratories overseeing prescription drug-monitoring programs. We present a case of sample adulteration in an attempt to conceal prescription non-compliance. The patient possessed only an active prescription for hydrocodone but on initial antibody-based screening the sample tested positive for benzodiazepines and oxycodone in addition to opiates. Active communication between the pain management clinic and the clinical laboratory alerted staff to conduct a more thorough investigation including sample validity testing, analyses of paired serum specimens by liquid chromatography tandem mass spectrometry. Analyses revealed the patient submitted a dilute urine specimen with a crushed hydrocodone pill inside in an attempt to hide prescription non-compliance. Previous screenings had been consistent with the medication list raising the question of whether this was an isolated incident or the patient had simply been more successful in manipulating specimens in the past. This case highlights the need for good communication among all members of the healthcare team and the widespread implementation of specimen validity testing for any laboratory that receives samples from pain clinics.