Nitrite Adulteration of Workplace Urine Drug-Testing Specimens I ...

study, including urinary tract infections and medications. It is
probable that the four specimens with nitrite concentrations in
excess of 100 tJg/mL were contaminated by enterobacteriaceae and
had sufficient nitrate present to achieve these levels. In contrast to
these specimens, which were allowed to incubate at room tem-
perature, 15 other drug-negative specimens were selected at
random from 60 in an initial test batch and tested for nitrite con-
centration. The data are not contained in the table because all 15
were below the limit of detection of the method, 0.6 IJg/mL. These
data illustrate that specimens more typical of the age of workplace
drug-testing specimens, 12-24 h, tend to be negative or have low
concentrations of nitrite, whereas those that are allowed to incu-
bate can reach concentrations relatively high for nonadulterated
specimens.
94
Table IV. Nitrite Concentrations in Urine Specimens
Received for Employment Drug Testing which were
Initial Test Negative and Held at Room Temperature for
2-3 Weeks
Nitrite (pg/mL)
Specimen No. 2weeks 3weeks
1 19.7 33.8
2 121.2 121.2
3 37.1 36.8
4 43.0 37.4
5 6.9 7.2
6 34.8 33.8
7 122.2 118.6
8 43.0 39.7
9 6.9 7.2
10 34,2 36.1
11 128.1 129.1
12 42.7 37.8
13 6.2 7.2
14 43.7 36.4
15 63.7 116.9
Average 50.2 53.3
Range 6.2-128.1 7.2-129.I
Table V. Sources of Nitrite in Urine and Approximate
Concentrations Achievable From Them*
Source Approximate nitrite concentration (pg/mL)
Internal sources
Urinary tract infection 150
Palhological conditions 100
Normal biochemistry Trace
External source.g
Medications 25
All other natural sources
Food, water, air,
occupational exposure,
induction by medications