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Title 42Chapter IVSubchapter GPart 493Subpart I → §493.933

Title 42: Public Health
Subpart I—Proficiency Testing Programs for Nonwaived Testing

§493.933   Endocrinology.

(a) Program content and frequency of challenge. To be approved for proficiency testing for endocrinology, a 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 patient specimens. 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, blood, or urine samples.

Analyte or Test


Free Thyroxine

Human Chorionic gonadotropin (excluding urine pregnancy tests done by visual color comparison categorized as waived tests)

T3 Uptake


Thyroid-stimulating hormone


(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 (5) of this section.

(1) To determine the accuracy of a laboratory's response for qualitative and quantitative endocrinology tests or analytes, a 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 endocrinology is either the score determined under paragraph (c)(2) or (c)(3) of this section.

(2) For quantitative endocrinology 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 either fixed criteria based on the percentage difference from the target value or the number of standard deviations (SDs) the response differs from the target value.

Criteria for Acceptable Performance

The criteria for acceptable performance are—

Analyte or test Criteria for acceptable performance
CortisolTarget value ±25%.
Free ThyroxineTarget value ±3 SD.
Human Chorionic Gonadotropin (excluding urine pregnancy tests done by visual color comparison categorized as waived tests)Target value ±3 SD positive or negative.
T3 UptakeTarget value ±3 SD.
TriiodothyronineTarget value ±3 SD.
Thyroid-stimulating hormoneTarget value ±3 SD.
ThyroxineTarget value ±20% or 1.0 mcg/dL (greater).

(3) The criterion for acceptable performance for qualitative endocrinology tests is positive or negative.

(4) 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

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(5) 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

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

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