';


Title 42 Part 493 → Subpart I → §493.937

Title 42 → Chapter IV → Subchapter G → Part 493 → Subpart I → §493.937

Electronic Code of Federal Regulations e-CFR

Title 42 Part 493 → Subpart I → §493.937

e-CFR data is current as of January 16, 2020

Title 42Chapter IVSubchapter GPart 493Subpart I → §493.937


Title 42: Public Health
PART 493—LABORATORY REQUIREMENTS
Subpart I—Proficiency Testing Programs for Nonwaived Testing


§493.937   Toxicology.

(a) Program content and frequency of challenge. To be approved for proficiency testing for toxicology, the annual program must provide a minimum of five samples per testing event. There must be at least three testing events at approximately equal intervals per year. The annual program must provide samples that cover the clinically relevant range of values that would be expected in specimens of patients on drug therapy and that cover the level of clinical significance for the particular drug. The samples may be provided through mailed shipments or, at HHS' option, may be provided to HHS or its designee for on-site testing.

(b) Challenges per testing event. The minimum number of challenges per testing event a program must provide for each analyte or test procedure is five serum, plasma, or blood samples.

Analyte or Test Procedure

Alcohol (blood)   Phenytoin
Blood lead   Primidone
Carbamazepine   Procainamide
Digoxin      (and metabolite)
Ethosuximide   Quinidine
Gentamicin   Theophylline
Lithium   Tobramycin
Phenobarbital   Valproic Acid

(c) Evaluation of a laboratory's analyte or test performance. HHS approves only those programs that assess the accuracy of a laboratory's responses in accordance with paragraphs (c)(1) through (4) of this section.

(1) To determine the accuracy of a laboratory's responses for quantitative toxicology tests or analytes, the program must compare the laboratory's response for each analyte with the response that reflects agreement of either 80 percent of ten or more referee laboratories or 80 percent or more of all participating laboratories. The score for a sample in toxicology is the score determined under paragraph (c)(2) of this section.

(2) For quantitative toxicology tests or analytes, the program must determine the correct response for each analyte by the distance of the response from the target value. After the target value has been established for each response, the appropriateness of the response must be determined by using fixed criteria based on the percentage difference from the target value

Criteria for Acceptable Performance

The criteria for acceptable performance are:

Analyte or test Criteria for acceptable performance
Alcohol, bloodTarget Value ±25%.
Blood leadTarget Value ±10% or 4 mcg/dL (greater).
CarbamazepineTarget Value ±25%.
DigoxinTarget Value ±20% or ±0.2 ng/mL (greater).
EthosuximideTarget Value ±20%.
GentamicinTarget Value ±25%.
LithiumTarget Value ±0.3 mmol/L or ±20% (greater).
PhenobarbitalTarget Value ±20%
PhenytoinTarget Value ±25%.
PrimidoneTarget Value ±25%.
Procainamide (and metabolite)Target Value ±25%.
QuinidineTarget Value ±25%.
TobramycinTarget Value ±25%.
TheophyllineTarget Value ±25%.
Valproic AcidTarget Value ±25%.

(3) To determine the analyte testing event score, the number of acceptable analyte responses must be averaged using the following formula:

eCFR graphic er25se06.023.gif

View or download PDF

(4) To determine the overall testing event score, the number of correct responses for all analytes must be averaged using the following formula:

eCFR graphic er25se06.022.gif

View or download PDF

[57 FR 7151, Feb. 28, 1992, as amended at 58 FR 5229, Jan. 19, 1993; 68 FR 3702, Jan. 24, 2003]