Main Body

Clinical Chemistry and Hematology Laboratories

About Clinical Chemistry at the Wadsworth Center

All summary data from urine pregnancy proficiency tests (February 1998 - present) are available on line. Go to the Urinalysis and Urine Pregnancy Proficiency Test Data Base

Urinalysis Proficiency Testing

Laboratories performing qualitative or semi-quantitative analysis of urinary glucose, protein, ketones, pH, hemoglobin, bilirubin and measurement of specific gravity should apply for this permit category. Other quantitative urine testing is performed under appropriate subcategories of Clinical Chemistry or Toxicology.

Survey samples are prepared in-house using synthetic urine as the base matrix. Constituents are quantitatively transferred to the matrix. Each survey consists of a series of samples in sealed vials with concentrations encompassing the clinically relevant ranges. Analytes included in the testing program are as follows: glucose, protein, ketones, hemoglobin, bilirubin, pH and specific gravity.

Samples with preservatives and stabilizers that do not interfere with analyses are distributed frozen. Specimens are assayed within our laboratory for tested analytes from representative vials to assess sample-to-sample variability.

Theoretical targets (weighed-in values) are compared against the participant distribution of results. The information is used to determine the correct response for all required analytes. For pH and specific gravity reasonable ranges around the participant mean are used to grade participant results. All other analytes are graded on a consensus participant result with appropriate acceptable limits. Certain analytes are verified by quantitative analysis.

Target values for this specialty are determined by participant data and theoretical levels of added analytes.

GRADING

For urinalysis, this will involve the following: Number of acceptable responses for the analyte x 100 = Analyte Score

Total number of challenges for the analyte

Number of acceptable responses for all challenges x 100 = Testing Event Score

Total number of challenges

An analyte score of 80% or greater is considered acceptable performance for a proficiency test event. Any test event analyte failure (i.e. a score of less than 80%) places a laboratory at risk of overall failure for that analyte for two subsequent surveys.

Laboratories that fail to achieve a passing score for an analyte in two consecutive test events or two out of three events are required to perform corrective action and complete a remediation program for that analyte. Remediation programs are designed specifically for each laboratory based upon the nature of the proficiency test failure.

Urine Pregnancy Proficiency Testing

Laboratories should hold this category if they are performing urine pregnancy testing. Serum pregnancy testing is included in the Endocrinology category.

A synthetic urine matrix, prepared in-house, is used for these samples. Human chorionic gonadotropin is added to this base in concentrations encompassing the sensitivity levels of various kits used by participating laboratories.

Samples with preservatives and stabilizers that do not interfere with analyses are distributed frozen. Specimens are assayed both quantitatively and qualitatively within our laboratory for human chorionic gonadotropin from representative vials to assess sample-to-sample variability.

Target values for human chorionic gonadotropin are determined quantitatively and used as the basis for the scoring scheme described under Sample Validation below. Participant data is reviewed to ascertain that the qualitative screening methods are in agreement with the weighed-in and quantitated values.

GRADING

For urine pregnancy this will involve the following:

Number of acceptable responses for the analyte x 100 = Analyte Score
Total number of challenges for the analyte.

Determination of the correct result for each test sample in this specialty is determined as follows:

	CONDITION	+	-	?
T.V. > CO + 5mIU/rnL	*
T.V. > CO and T.V. < CO + 5rnIU/mL	*		*
T.V. < CO and T.V. < 20 mIU/mL	*	*	*
T.V. < CO and CO - T.V. > 20 mumIU/mL		*	*

ABBREVIATIONS

The correct answer(s) for each condition are indicated with a (*) star. T.V. (True Value) = The hCG content(mIU/mL) of the proficiency specimen. CO (Positive Cutoff) = The positive cutoff in mIU/mL reported by the lab.

Please mail comments, corrections or suggestions to: clinchem@wadsworth.org