Jul 28, 1989 - P, Gross. SJ. Active and realistic passive marijuana exposure tested by three immunoassays ... In: Peter RC, ed. NIDA Res Monogr Ser 31.
lower than the total cannabinoid units measured by any immunoassay procedure. The concentration of this major metabolite by gas chromatography was about 31% of the value obtained by RLA (Abuscreen) and about 48.9% of the value obtained by EIA enzyme immunoassay (EMIT-d.a.u.), but standard deviations for the comparison were 11.7% and 19.2%, respectively, indicating wide sample-to-sample variation. A retrospective review of these data shows that of the reported total of 29 samples, 14 (48%) would have been declared positive by RIA but only ii (38%) by EMIT if a 100 g/L cutoff threshold had been used. Moreover, another laboratory has recently described a significant difference in positive results for EMIT cannabinoid testing, compared with the Immunalysis RIA system at the 100 .tg/L cutoff (10). Thus, our data confirm the findings of others that, even at the relatively high threshold of 100 ugfL, the proportion of positive specimens actually found to be positive is technique dependent. The purpose of this report is not to recommend any one immunoassay technique as superior to another but rather to point out the limitations of comparing data obtained with two or more of these techniques. Considerable confusion can arise when different laboratories compare results for the same specimen by different methods or when performances on proficiency survey specimens are compared. Antibody specificity, calibrator, and (or) tracer chemical structure differ for each assay. Reportedly, 35 or more different cannabinoid metabolites are present in urine after marijuana use (11). These metabolites demonstrably cross-react in an RIA (12); presumably other assays would demonstrate their own specific pattern of cross-reactivity. Individual variations among drug users in metabolite production as well as differences in antibody reactivity among assays are likely to yield different results for the same set of specimens, even if the same calibrator or cannabinoid
compounds
Clinical
laboratories,
are
CLIN. CHEM. 35/11, 2243-2247
Changes Transport
used
unlike
to standardize
forensic
the
laboratories,
assay.
have
a
1. Mule
SJ,
Lomax
P,
Gross
SJ.
Active
D. P. Taggart,2
‘Institute of Clinical Surgery, and’ Department G4 OSF,
April
and
realistic
passive
marijuana exposure tested by three immunoassays and GC/MS in urine. J Anal Toxicol 1988;12:113-6. 2. Moffatt AC, Williams PL, King U. Combined high-performance liquid chromategraphy and radioimmunoasaay method for the analysis of delta-9-tetrahydrocannabinol and its metabolites in plasma and urine. In: Hawks RL, ed. NIDA Res Monogr Ser 42. Rockville, MD: National Institute on Drug Abuse, 1982:56-8. 3. Fredrick DL, Green J, Fowler MW. Comparison of six cannabinoid metabolite assays. J Anal Toxicol 1985;9:116-20. 4. Sutheimer CA, Yarborough R, Hepler BR, Sunshine I. Detection and confirmation of urinary cannabinoids. J Anal Toxicol 1985;9:156-60. 5. Jones AB, ElSohly HN, Arafat ES, ElSohly MA. Analysis of the major metabolite of delta-9-tetraliydro-cannabinol in urine. IV. A comparison of five methods. J Anal Toxicol 1984;8:249-51. 6. Irving J, Leeb B, Foltz RL, Cook JT, Bursey RE, Willette RE. Evaluation of immunoassays for cannabinoids in urine. J Anal Toxicol 1984;8:192-6. 7. Black BL, Goldberger BA, Isenchnoid SM, White SM, Caplan YH. Urine cannabinoid analysis: an integrated multi-method approach. J Anal Toxicol 1984;8:224-7.
Fed Reg. Vol 53, No. 69. April 11, 1988. MA, ElSohly HN, Jones AB, Dimson PA, Wells KE. of the major metabolite of delta-9-tetrahydro-canin urine. H. A HPLC procedure. J Anal Toxicol 1983;7:262-4. 10. Berkabile DR, Meyer A. False negative rate for EMiT cannabinoids [Letterl. J Anal Toxicol 1989;13:63. 11. Peterson RC. Marijuana research findings: 1980. In: Peter RC, ed. NIDA Res Monogr Ser 31. Rockville, MD: National Institute on Drug Abuse, 1980:13. 12. Jones AB, ElSohly HN, ElSohly MA. Analysis of the major metabolite of delta-9-tetrahydrocannabinoid in urine. V. Croasreactivity of selected compounds in a radioirnmunoasaay. J Anal Toxicol 1984;8:252-4. 8.
9. ElSohly Analysis nabinoid
(1989)
G. S. Fell,’ T. D. B. Lyon,1 D. Wheatley,’
Concentrations of iron, zinc, and copper and of their respective transport proteins transferrin, albumin, and ceruloplasmm were measured in serum after elective cholecystectomy and cardiac surgery. The pattern of changes in the concentrations of iron, zinc, and copper was reproducible, with an early increase in serum iron and zinc, then a decrease in the concentrations as these metals are dissociated from their serum transport proteins. Zinc and iron concentrations change before the increase in C-reactive protein, which be-
Received
References
in Iron, Zinc, and Copper Concentrations in Serum and in Their Proteins after Cholecystectomy and Cardiac Surgery
W. D. Fraser,’
Glasgow
variety of motivations for using a particular cannabinoid screening and confirmation technique. Adoption of a single positive detection threshold will not provide equivalent evaluation of cannabinoid use when tested with different immunoassay screening techniques.
Biochemistry,
2
of Surgery,
Department
Glasgow
U.K.
14, 1989; accepted
July
28,
of
Royal 1989.
Cardiac
Infirmary,
0. J. Garden,3
Binding
to
and A. Shenkln’
gins 8 h after incision, whereas the copper concentration in the serum remains constant in the early postoperative period. Quantitative and kinetic differences were observed in both the trace metal and protein changes after cardiac surgery and cholecystectomy. These studies indicate the complexity of interpreting changes in trace elements in serum after surgery. AddItional C-reactive
Keyphrases: protein
transferrin trace elements
albumin
ceruloplasmin
The
acute-phase response has been described (1) as “an unspecific, but highly complex reaction of an animal organism to a variety of injuries such as bacterial infection, mechanical or thermal trauma, malignant growth or isearly
CLINICAL
CHEMISTRY,
Vol.35,
No. 11, 1989
2243
chaemic proposed, endocrine
necrosis.” Several mediators of this have been and evidence has accumulated that multiple and humoral events trigger the biochemical and physiological changes of the acute-phase response (2-4). Positive and negative acute-phase reactants have been identified and their temporal relationships defined (5, 6). To date, however, few differences have been noted in the magnitude of the acute-phase response in terms of changes in protein and trace metal concentrations after different surgical procedures. Colley et al. (5) found that the increase in C-reactive protein (CRP) usually is not proportional to the severity of the trauma. In this study, we have compared the acute-phase response observed after two markedly different operations, cholecystectomy and cardiac surgery, by taking multiple blood samples, which we used to investigate changes in trace metals and proteins during the pre-operative and postoperative periods.
to the normal reference interval in either group during the study. The zinc:albumin ratio returned to the reference interval by 24 h after incision in the cholecystectomy group but not until 96 h in the cardiac surgery group. Figure 2 shows the alterations in CRP and ceruloplasmin concentrations over the seven-day period. CRP concentrations had not returned to within the reference interval (
