ASCP Laboratory Operations 2 — Questions and Answers

Question 1: In Westgard rules for quality control, the 1:3s rule means:

Ten consecutive QC values on the same side of the mean
One QC result exceeds 3 standard deviations from the mean — reject the run (Correct answer)
Two consecutive QC results exceed 2 standard deviations
Four consecutive results exceeding 1 standard deviation in the same direction

Correct answer: One QC result exceeds 3 standard deviations from the mean — reject the run

The 1:3s rule is a rejection rule: if any single QC result falls outside mean plus or minus 3 SD, the run is rejected. This primarily detects random error with high probability of error detection and a low false rejection rate.

Westgard multirule QC combines multiple rules to maximize error detection while minimizing false rejections. Commonly used rules: 1:3s (reject — random error), 2:2s (reject — systematic error: two consecutive QC above +2s or below -2s), R:4s (reject — random error: one QC above +2s and another below -2s in same run), 4:1s (warning or reject — systematic error: four consecutive above 1s in same direction), 10:x-bar (systematic error: ten consecutive on same side of mean). The 1:2s is a warning rule that triggers evaluation but not automatic rejection.

Question 2: Reference interval verification in a new laboratory minimally requires:

200 healthy reference subjects
At least 20 healthy subjects when adopting manufacturer or published reference intervals (Correct answer)
500 patients with known diagnoses
No validation if using FDA-cleared reagents

Correct answer: At least 20 healthy subjects when adopting manufacturer or published reference intervals

CLSI EP28-A3c allows reference interval verification (not full establishment) with a minimum of 20 healthy reference individuals. If 2 or fewer of 20 results fall outside the claimed reference interval, the interval is considered verified for that population.

CLSI EP28 guidance: Full reference interval establishment requires 120 or more healthy reference subjects using parametric or nonparametric statistics to determine the 2.5th and 97.5th percentiles. Verification (adopting manufacturer or published intervals) requires 20 or more subjects. Pass: 2 or fewer of 20 outside claimed interval. Fail: 3 or more of 20 outside, requiring investigation and either adjusted limits or full establishment. Transference for the same method, same population at a different site allows a smaller verification study. Pediatric and geriatric reference intervals require age- and sex-stratified subjects.

Question 3: The delta check in laboratory medicine is designed to detect:

Analytical errors in the QC material
Significant changes in a patient's results that may indicate specimen mislabeling or acute clinical change (Correct answer)
Reagent lot-to-lot variation
Instrument calibration drift

Correct answer: Significant changes in a patient's results that may indicate specimen mislabeling or acute clinical change

A delta check compares a patient's current result to a previous result within a defined time window. An unexpected delta (change greater than established limits) triggers investigation for specimen mislabeling (most common cause) or a true rapid clinical change.

Delta check formula: absolute value of (current minus previous) divided by previous times 100% as percentage change, or as absolute difference. Examples: sodium delta above 10 mEq/L in 24 hours, potassium delta above 1.5 mEq/L, and hemoglobin delta above 2 g/dL in 24 hours. If delta is exceeded: verify specimen identity including collection tube and patient ID, and check for hemolysis, lipemia, or draw from IV line. Studies show delta checks on blood type results are the most effective use — ABO discrepancy between current and previous results reliably detects mislabeling.

Question 4: Which ISO standard is specifically designed for medical laboratory quality management?

ISO 9001
ISO 15189 (Correct answer)
ISO 14001
ISO 27001

Correct answer: ISO 15189

ISO 15189 is the international standard specifically for medical laboratories, addressing quality management and technical competence. It is based on ISO 17025 (testing laboratories) but adapted for the unique requirements of clinical laboratory medicine.

ISO 15189 (Medical laboratories — Requirements for quality and competence) covers management requirements including organization, quality management system, document control, service agreements, examination of external laboratories, advisory services, complaints, nonconformities, and corrective and preventive action; and technical requirements including personnel, accommodation, pre-examination, examination, post-examination processes, and reporting. Accreditation by bodies like CAP and UKAS demonstrates ISO 15189 compliance. In the US, CAP accreditation exceeds CLIA minimum requirements and aligns with ISO 15189.

Question 5: When a critical (panic) value is generated for a patient, what is the immediate required action?

Repeat the test before taking any action
Immediately notify the responsible healthcare provider and document the communication (Correct answer)
Report the result in the LIS and wait for the provider to see it
Call the patient directly

Correct answer: Immediately notify the responsible healthcare provider and document the communication

CLIA requires immediate notification of responsible clinical personnel when critical values are obtained. The laboratory must notify the provider or designee, document the date, time, result, and name of person notified. Documentation is mandatory.

Critical value policy requirements: list of critical values established by medical director with clinicians; immediate notification typically within 30–60 minutes of result verification; direct verbal communication with read-back preferred; documentation in LIS of result, time notified, name of notifier, name of person notified, and read-back confirmation. CAP checklist requires documentation of timeliness. Repeat testing before reporting is not required for most critical values if QC is in control, though verification of specimen integrity is prudent.

Question 6: Root cause analysis (RCA) in the laboratory is conducted primarily to:

Assign blame to the technologist who made the error
Identify the fundamental system or process failures that allowed an error to occur and prevent recurrence (Correct answer)
Document errors for regulatory inspection purposes only
Discipline employees who deviate from procedure

Correct answer: Identify the fundamental system or process failures that allowed an error to occur and prevent recurrence

RCA is a non-punitive, systematic process to identify the root causes (not just proximate causes) of errors. The goal is process improvement and error prevention through system-level changes rather than individual blame.

RCA methodology often uses the Five Whys approach or a fishbone (Ishikawa) diagram to work backward from the error and identify contributing factors categorized as people, process, equipment, environment, materials, and management. The non-punitive Just Culture model distinguishes human error (system fix), at-risk behavior (coaching), and reckless behavior (accountability). RCA should lead to procedure revision, training enhancement, system barriers such as double-checks and alerts, and environmental changes. FMEA (Failure Mode and Effects Analysis) is the prospective complement — identifying potential failures before they occur.

ASCP Laboratory Operations 2

In Westgard rules for quality control, the 1:3s rule means: