Updated directive makes parameters clearer
December 1, 2000 3 minutes read
Updated directive makes parameters clearer
The recent investigation of drug-testing laboratories by the federal government centered on whether the labs were complying with the most current version of the federal standards for testing samples.
The U.S. Department of Health and Human Services issued National Laboratory Certification Program Directive 35, known as PD 35, on Sept. 28, 1998. That directive outlined the specific manner in which certified labs would test urine samples and the parameters under which the lab may declare a sample adulterated or substituted. The requirements were updated on July 28, 1999, with PD 37.
Unlike many federal standards and regulations, PD 37 did not come with a deadline for implementing the changes. As a result, federally certified labs could update their procedures at their own pace. In the recent dispute with Delta Air Lines, LabOne in Lenexa, KS, contends that it updated its procedures as quickly as possible, complying with PD 37 in January 2000.
Regarding the possible adulteration or substitution of urine samples, PD 37’s significant change is that the lab must test two aliquots of the urine sample. Other changes address the manner in which results are reported, but the specific cutoffs for determining when a specimen is substituted were not changed. These are excerpts from PD 35 and the updated PD 37:
PD 35: "A laboratory may determine for each specimen (i.e., from either a single specimen collection or the primary specimen [Bottle A] from a split specimen collection) the nitrite concentration, creatinine concentration, specific gravity, and pH. These tests shall follow scientifically suitable methods and produce results, which are accurately quantified."
The sample is defined as "substituted (i.e., the specimen does not exhibit the clinical signs or characteristics associated with normal human urine) if the creatinine concentration is < 5 mg/dl and the specific gravity is < 1.001 or > 1.020."
PD 37: "Specimen validity can be determined by establishing parameters that are consistent with normal human urine and/or by testing for the presence of abnormal or foreign substances in the urine. Specimen validity testing may be conducted on Bottle A and must be conducted on Bottle B if Bottle B fails to reconfirm for the requested drug/analyte."
"For substituted specimens, at a minimum, creatinine must be measured by at least one quantitative procedure on two different aliquots both utilizing the specified cutoff of < 5 mg/dL. At a minimum, specific gravity must be performed on one of these aliquots utilizing the specified cutoffs of < 1.001 or > 1.020.
"Truncating a quantitative value has been acceptable with >, >, and < decision points or cutoffs. However, truncating a quantitative value is not acceptable with < decision points or cutoffs. In < scenarios, truncating would change the result from acceptable to unacceptable (e.g., truncating a pH reading of 3.2 to 3 or a creatinine reading of 5.4 mg/dL to 5 mg/dL).
"Values from tests for creatinine (< 5 mg/dL) or pH (< 3) should contain one significant decimal place more than that specified in the stated decision point.
"For specific gravity (< 1.001), the method must measure to the third (3rd) decimal place. This will require refractometry because spectrophotometric and paper/stick’ procedures are not sensitive enough to accurately discriminate in that range."
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