LMPG: Laboratory Support
for Emergency Toxicology
(Draft Guidelines)
Part
III. Recommendations
for BREATH ALCOHOL ANALYSIS
A.
Need for a QA/QC Program
Portable and bench-top breath alcohol devices have been available for many
years and are widely used for traffic law enforcement.
Current alcohol breath analyzers are accurate, precise, and
inexpensive.
As a result, many emergency departments have adopted breath meters
for determining bedside alcohol concentrations in intoxicated patients.
Currently, the Health Care Finance Administration (HCFA) and the
Clinical Laboratory Improvement Act 1988 (CLIA 88) does not regulate
breath alcohol testing because a discrete sample is not collected and
separately analyzed (the exhalation of breath directly into a device does
not constitute a sample collection).
Thus in the manner that a pulse oximeter measurement is not subject
to CLIA 88 regulations, neither is breath alcohol measurement.
Nevertheless, due to the importance of alcohol measurement, the
Committee feels that laboratory oversight is necessary.
The recommendations that follow were formulated by a Task Force of
the American Association for Clinical Chemistry, Therapeutic Drug
Monitoring and Clinical Toxicology Division (39).
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Discussion
Elements of
an effective QA program include monitoring and evaluating the overall
quality of the total testing process (pre-analytic, analytic and
post-analytic steps) as well as the evaluation of effectiveness of
policies and procedures, identification and correction of problems,
assurance of accurate, reliable, and prompt reporting of test results, and
affirming the competency of operators.
It is necessary to have a comprehensive up-to-date accessible
Standard Operating Procedure (SOP) manual, operator training and
evaluation of competency, and a QC program.
Each device must be checked for accuracy each day by use of a dry
gas standard and an air blank. The recover of alcohol must be within the
tolerance established by the manufacturer.
The essential operator procedures are listed in Table 3.
Table 3. Essential Operator Procedures for Breath Alcohol Analysis
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Use of test device under manufacturer recommended environmental conditions
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Use of a properly calibrated device
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Verification that the blank and alcohol accuracy (QC) recoveries are within specifications
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Use of an air check or blank breath test immediately prior to the patient test
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Confirmation of patient identification
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Observation of the patient to ascertain that residual alcohol and foreign objects are cleared from the mouth
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Instruction of patient on proper delivery of a deep-lung sample
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Documentation of test date, time, device, QC result, patient ID and results
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Prompt and accurate reporting of results.
Given that breath alcohol analyzers are point-of-care testing devices, the same requirements and principles and responsibilities that govern POCT should also be applicable. Clinical laboratory personnel are the most experienced, trained, and qualified to evaluate analytical performance such as precision, accuracy, reliability, sensitivity and specificity.
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Discussion
The
selection of breath alcohol devices should be based on performance and
features that meet the requirements of clinical services.
Only devices listed in the National Highway Traffic Safety
Administration (NHTSA) Conforming Product List should be used (40).
Table 4 lists the Committee’s recommendation for specific device
specifications and desirable attributes for breath alcohol measurements in
the ED.
Table 4. Device Specifications and Desirable Attributes for Point-of Care Breath Alcohol Analysis
Device specifications
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Accuracy and precision should meet or exceed performance required for intended clinical use
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Prevents false positive results from acetone (up to 0.02% w/v)
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Clinically appropriate analytical (reportable range in units of grams alcohol/100 mL of blood)
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Environmental conditions appropriate for operation
Desirable attributes
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Mistake-proof for ease of use by non-laboratory personnel
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Procedural controls that monitor requisite operator steps and specimen delivery
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Function checks that monitor components performance
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Data logging capability
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Printer and/or laboratory information management system interface
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Battery operated devices should have a "low battery" indicator
The
clinical laboratory has the responsibility to validate that the device
performance meets or exceeds specifications prior to release of the
technology for clinical use at near-patient sites.
This includes familiarization with the technology using
vendor-supplied educational materials or programs, and adjust manufacture
guidance to clinical service requirements.
Verification of device performance characteristics requires use of
NHTSA-approved breath alcohol simulator and certified alcohol solutions or
certified dry gas alcohol standards.
The analytical performance should be evaluated against experimental
protocols established by the National Committee on Clinical Laboratory
Standards (NCCLS)(41).
The accuracy and precision studies should be performed at
clinically relevant alcohol concentrations.
The specificity should be challenged with aqueous solutions of
volatiles (acetone, methanol, isopropanol) at concentrations likely to be
encountered in clinical settings.
The calibration stability should be verified with suitable QC
materials for each day the device is used.