Drugs of Abuse Screen 5, Chain of Custody, Meconium
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Illicit drug use during pregnancy is a major social and medical issue. Drug abuse during pregnancy is associated with significant perinatal complications, which include a high incidence of stillbirths, meconium-stained fluid, premature rupture of the membranes, maternal hemorrhage (abruption placenta or placenta praevia), and fetal distress.(1) In the neonate, the mortality rate, as well as morbidity (eg, asphyxia, prematurity, low birthweight, hyaline membrane disease, infections, aspirations pneumonia, cerebral infarction, abnormal heart rate and breathing patterns, drug withdrawal) are increased.(1)
The disposition of drug in meconium is not well understood. The proposed mechanism is that the fetus excretes drug into bile and amniotic fluid. Drug accumulates in meconium either by direct deposit from bile or through swallowing of amniotic fluid.(2) The first evidence of meconium in the fetal intestine appears at approximately the 10th to 12th week of gestation, and slowly moves into the colon by the 16th week of gestation.(3) Therefore, the presence of drugs in meconium has been proposed to be indicative of in utero drug exposure during the final 4 to 5 months of pregnancy, a longer historical measure than is possible by urinalysis.(2)
Chain of custody is a record of the disposition of a specimen to document who collected it, who handled it, and who performed the analysis. When a specimen is submitted in this manner, analysis will be performed in such a way that it will withstand regular court scrutiny.
Identifying amphetamines (and methamphetamines), opiates, as well as metabolites of cocaine and marijuana in meconium specimens
Chain of custody is required whenever the results of testing could be used in a court of law. Its purpose is to protect the rights of the individual contributing the specimen by demonstrating that it was under the control of personnel involved with testing the specimen at all times; this control implies that the opportunity for specimen tampering would be limited. Since the evidence of illicit drug use during pregnancy can be cause for separating the baby from the mother, a complete chain of custody ensures that the test results are appropriate for legal proceedings.
The limit of quantitation varies for each of these drug groups.
-Amphetamines: >100 ng/g
-Methamphetamines: >100 ng/g
-Cocaine and metabolite: >100 ng/g
-Opiates: >100 ng/g
-Tetrahydrocannabinol carboxylic acid: >20 ng/g
-Phencyclidine (PCP): >20 ng/g
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
If heroin use is suspected, specimen must be sent frozen to prevent loss of 6-monoacetylmorphine (6MAM, heroin metabolite). When refrigerated, a significant percentage of 6MAM will convert to morphine in fewer than 24 hours.
Unless sent frozen, cocaine metabolite, m-hydroxybenzoylecgonine, will degrade within 72 hours of collection.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Positives are reported with a quantitative LC-MS/MS result.
Amphetamines by ELISA: 100 ng/g
Methamphetamine by ELISA: 100 ng/g
Benzoylecgonine (cocaine metabolite) by ELISA: 100 ng/g
Opiates by ELISA: 100 ng/g
Tetrahydrocannabinol carboxylic acid (marijuana metabolite) by ELISA: 20 ng/g
Phencyclidine by ELISA: 20 ng/g
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Ostrea EM Jr: Understanding drug testing in the neonate and the role of meconium analysis. J Perinat Neonatal Nurs 2001 Mar;14(4):61-82; quiz 105-106
2. Ostrea EM Jr, Brady MJ, Parks PM, et al: Drug screening of meconium in infants of drug-dependent mothers; an alternative to urine testing. J Pediatr 1989 Sep;115(3):474-477
3. Ahanya SN, Lakshmanan J, Morgan BL, Ross MG: Meconium passage in utero: mechanisms, consequences, and management. Obstet Gynecol Surv 2005 Jan;60(1):45-56; quiz 73-74