Page Last Updated: October 16, 2025

USDTL Nails Toxicology (Maternal)šŸ”—

Table Name:
bio_bm_biosample_nails_results (toxicology screen), bio_bm_biosample_nails_type (specimen type)
Construct:
Drug, Environmental Exposure
Data Warning ā–ø

Continuous Variables
For all toxicology screens, continuous variables should be interpreted with caution based on the threshold limits of quantification (LOQs), or the cutoff concentration used to categorize metabolites as positive or negative. LOQs are provided in Table 1. Nail Assay Thresholds.

Updated Workflow
As of July 1, 2024, the nail processing workflow was updated to optimize specimen use and allow confirmation testing for low sample quantities. Prior to this update, remnants of ELISA extract were not used for confirmation when specimens had insufficient sample.

Large Gaps Between Collection and Analysis Dates
A substantial number of samples show unusually long intervals between collection and analysis (e.g., over 100ā€“300 days, compared to the 30-day limit specified by internal SOPs). We are working to determine whether this reflects a data entry or site-level issue and will provide an update once more information is available.

Administration & Quality ControlšŸ”—

Respondent Pregnant/postpartum person
Administration Self-collected under research team supervision, or collected by research team
Visits V01, V02
Completion Time 5 min
Quality Control Examine assay ranges and categorical versus continuous measures.

Instrument DetailsšŸ”—

For the USDTL assay, fingernail and toenail specimens are sorted by weight, and those weighing at least 20 mg undergo ELISA screening, followed by LCMSMS confirmation for presumptive positives, each requiring an additional 20 mg. If insufficient specimen remains for LCMSMS, the remnant ELISA extract is used for confirmation.

Based on the predefined threshold outlined in Table 1, a confirmatory test result for any substance analyte is determined to be positive, negative, or invalid (QNS i.e. quantity not sufficient). Substance analytes (e.g. Amphetamine (c_amp_n)) are grouped into different classes by analyte screening tests and confirmatory tests (Table 2).

Table 1. Nail Assay Thresholds ā–ø
Analyte LOD Limit of detection (pg/mL) LOQ Limit of quantification (pg/mL) Cutoff (pg/mL) Detection Window (months)
Amphetamine 20 40 100 Finger 3-6; Toe 10-14
Methamphetamine 20 40 100 Finger 3-6; Toe 10-14
MDA 20 40 100 Finger 3-6; Toe 10-14
MDMA 20 40 100 Finger 3-6; Toe 10-14
MDEA 20 40 100 Finger 3-6; Toe 10-14
Carboxy-delta-9-THC 0.01 0.02 0.05 Finger 3-6; Toe 10-14
Cocaine 20 40 100 Finger 3-6; Toe 10-14
Cocaethylene 10 20 50 Finger 3-6; Toe 10-14
Benzoylecgonine 10 20 50 Finger 3-6; Toe 10-14
Norcocaine 10 20 50 Finger 3-6; Toe 10-14
6-MAM 20 40 100 Finger 3-6; Toe 10-14
Codeine 20 40 100 Finger 3-6; Toe 10-14
Hydrocodone 20 40 100 Finger 3-6; Toe 10-14
Hydromorphone 20 40 100 Finger 3-6; Toe 10-14
Morphine 20 40 100 Finger 3-6; Toe 10-14
Norhydrocodone 8 16 40 Finger 3-6; Toe 10-14
Oxycodone 20 40 100 Finger 3-6; Toe 10-14
Oxymorphone 20 40 100 Finger 3-6; Toe 10-14
Noroxycodone 8 16 40 Finger 3-6; Toe 10-14
Methadone 20 40 100 Finger 3-6; Toe 10-14
EDDP 20 40 100 Finger 3-6; Toe 10-14
Amobarbital 80 80 200 Finger 3-6; Toe 10-14
Butalbital 80 80 200 Finger 3-6; Toe 10-14
Pentobarbital 80 80 200 Finger 3-6; Toe 10-14
Phenobarbital 80 80 200 Finger 3-6; Toe 10-14
Secobarbital 80 80 200 Finger 3-6; Toe 10-14
Alprazolam 20 40 100 Finger 3-6; Toe 10-14
Diazepam 20 40 100 Finger 3-6; Toe 10-14
Midazolam 20 40 100 Finger 3-6; Toe 10-14
Nordiazepam 20 40 100 Finger 3-6; Toe 10-14
Oxazepam 20 40 100 Finger 3-6; Toe 10-14
Temazepam 20 40 100 Finger 3-6; Toe 10-14
Ketamine 20 40 100 Finger 3-6; Toe 10-14
Norketamine 20 40 100 Finger 3-6; Toe 10-14
Tramadol 200 400 500 Finger 3-6; Toe 10-14
Fentanyl 2 4 10 Finger 3-6; Toe 10-14
Norfentanyl 2 4 10 Finger 3-6; Toe 10-14
Alfentanil 2 4 10 Finger 3-6; Toe 10-14
Acetyl Fentanyl 2 4 10 Finger 3-6; Toe 10-14
Acetyl Norfentanyl 2 4 10 Finger 3-6; Toe 10-14
Sufentanil 1 2 5 Finger 3-6; Toe 10-14
Norsufentanil 2 2 5 Finger 3-6; Toe 10-14
Buprenorphine 4 8 20 Finger 3-6; Toe 10-14
Norbuprenorphine 4 8 20 Finger 3-6; Toe 10-14
Ethyl glucuronide 4 8 20 Finger 3; Toe no consensus
Nicotine 20 40 100 Finger 3-6; Toe 10-14
Cotinine 20 40 100 Finger 3-6; Toe 10-14
Table 2. Mapping from Class to Screening Tests and Confirmatory Tests for Nails ā–ø
Class Screening Test Confirmatory Test
Stimulant (c_any_stim_n) amp/mamp (s_amp_n, s_mamp_n) Amphetamine (c_amp_n)
Methamphetamine (c_meth_n)
MDMA (c_mdma_n)
MDA (c_mda_n)
MDEA (c_mdea_n)
coc (s_coc_n) Cocaine (c_coc_n)
Cocaethylene (c_cocae_n)
Benzoylecgonine (c_ben_n)
Norcocaine (c_ncoc_n)
Cannabinoid (c_any_cannabinoid_n) thc (s_thc_n) Carboxy-delta-9-THC (c_delta-9-THC_n)
Barbiturate (c_any_barb_n) bar (s_bar_n) Amobarbital (c_amobarb_n)
Secobarbital (c_secobarb_n)
Pentobarbital (c_pentobarb_n)
Phenobarbital (c_phenobarb_n)
Butalbital (c_butalbital_n)
Benzodiazepine (c_any_benzo_n) benz (s_benz_n) Diazepam (c_diaz_n)
Oxazepam (c_oxaz_n)
Nordiazepam (c_nord_n)
Temazepam (c_tema_n)
Midazolam (c_mida_n)
Alprazolam (c_alpa_n)
Opioids (c_any_opioid_n) opi (s_opi_n) Codeine (c_cod_n)
Morphine (c_mor_n)
MAM (c_mam_n)
Hydrocodone (c_hydroc_n)
Norhydrocodone (c_norh_n)
Hydromorphone (c_hydrom_n)
mtd (s_mtd_n) Methadone (c_mtd_n)
EDDP (c_eddp_n)
oxyc (s_oxyc_n) Oxycodone (c_oxyc_n)
Noroxycodone (c_noxyc_n)
Oxymorphone (c_oxym_n)
tram (s_tram_n) Tramadol (c_tram_n)
fent (s_fent_n) Fentanyl (c_fent_n)
Norfentanyl (c_nfent_n)
Acetylfentanyl (c_acfent_n)
ActlNorfentanyl (c_acnfent_n)
suf (s_suf_n) Alfentanil (c_afent_n)
Sufentanil (c_suf_n)
Norsufentanil (c_nsuf_n)
bup (s_bup_n) Buprenorphine (c_bup_n)
Norbuprenorpine (c_nbup_n)
dissociative anesthetic (c_disanesth_n) ket (s_ket_n) Ketamine (c_ket_n)
Norketamine (c_nket_n)
Nicotine (c_nicotine_n) cot (s_cot_n) Nicotine (c_nic_n)
Cotinine (c_cot_n)
Ethanol (c_ethanol_n)   ethyl glucuronide (c_etoh_n)
Scoring Procedures ā–ø

Final results for each substance follows these rules:

  • If the confirmatory test for any substance analyte (e.g. Amphetamine (c_amp_n)) is positive based on predefined thresholds (Table 1), the class-level (c_any_stim_n) and sample-level (c_any_specimen_n) are also positive (value =1).
  • Otherwise, if the substance analyte confirmatory tests are negative, then class-level are negative (value =0). If all classes are negative (value = 0), then sample-level (c_any_specimen_n) are negative (value = 0).
  • Finally, if any substance analyte confirmatory tests are invalid (value = 3) then that class-level, and sample-level values are also invalid (value = 3)

Table 3. Screening Result Scoring

Level Result Type Example Options
Specimen Confirmatory results (presence of any analyte) c_any_specimen_n 1=positive; 0=negative; 3=invalid
Class Confirmatory results (presence of any analyte in class) c_any_stim_n 1=positive; 0=negative; 3=invalid
Analyte
 Screening results s_amp_n 1=positive; 0=negative; 3=invalid
Confirmatory results c_amp_n concentration value; -999
Confirmatory results - categorical c_amp_n_catCategorical confirmatory test variable for alcohol follows a different convention and is ā€˜c_ethanol_nā€™ 1=positive; 0=negative; 3=invalid; 4=screen negative

ReferencesšŸ”—

Bandoli, G., Anunziata, F., Bogdan, R., Zilverstand, A., Chaiyachati, B. H., Gurka, K. K., Sullivan, E., Croff, J., & Bakhireva, L. N. (2024). Assessment of substance exposures in nail clipping samples: A systematic review. Drug and Alcohol Dependence, 254, 111038. https://doi.org/10.1016/j.drugalcdep.2023.111038

Sullivan, E. L., Bogdan, R., Bakhireva, L., Levitt, P., Jones, J., Sheldon, M., Croff, J. M., Thomason, M., Lo, J. O., MacIntyre, L., Shrivastava, S., Cioffredi, L.-A., Edlow, A. G., Howell, B. R., Chaiyachati, B. H., Lashley-Simms, N., Molloy, K., Lam, C., Stoermann, A. M., ā€¦ HBCD Biospecimens Workgroup. (2024). Biospecimens in the HEALthy Brain and Child Development (HBCD) study: Rationale and protocol. Developmental Cognitive Neuroscience, 70(101451), 101451. https://doi.org/10.1016/j.dcn.2024.101451