Page Last Updated: May 14, 2026
USDTL Nails Toxicology (Maternal)🔗
| Table Name | bio_bm_biosample_nails_results (toxicology screen), bio_bm_biosample_nails_type (specimen type) |
| Construct | Drug Panel, Environmental Exposure |
| Study Visits | V01, V02 |
| Administration |
Respondent: Pregnant/postpartum person Method: Self-collected under supervision or collected by research team (5 min estimated duration) | Quality Control | Examine assay ranges and categorical versus continuous measures |
USDTL Screening Updates
As of November 2025, USDTL no longer assayed sufentanil in the nail samples.
Continuous Variables
Continuous variables should be interpreted with caution based on limits of quantification (LOQ), i.e. the minimum concentration at which metabolites can be reliably quantified. See Urine Assay Thresholds for Analytes.
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 100–300 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.
Interpretation of “QNS” in Confirmatory Results When a Positive Is Expected
In some cases, a specimen’s initial test meets the threshold for a positive result, but the confirmatory result is reported as “QNS” (Quantity Not Sufficient). This occurs when there is not enough specimen to conduct a confirmatory test or a confirmatory test must be repeated (following quality control procedures, e.g. unacceptable chromatography, poor recovery, or when a sample result is <5% of the previous specimen), but insufficient sample remains to complete the repeat test. Because the results could not be validated, this should be treated as a true quantity insufficiency.
Instrument Details🔗
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 thresholds (see Nail Assay Thresholds), 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 (see details).
The detection window for all analytes is 3-6 and 10-14 months for finger and toe nails, respectively, with the exception of Ethyl glucuronide (finger nails: 3; toe nails: no consensus).
| Analytes | LODLimit of detection / (pg/mL) | LOQLimit of quantification / (pg/mL) | CutoffThreshold used to classify results as positive or negative / (pg/mL) |
|---|---|---|---|
| Amphetamine / Methamphetamine | 20 | 40 | 100 |
| MDA / MDMA / MDEA | 20 | 40 | 100 |
| Carboxy-delta-9-THC | 0.01 | 0.02 | 0.05 |
| Cocaine | 20 | 40 | 100 |
| Cocaethylene / Benzoylecgonine / Norcocaine | 10 | 20 | 50 |
| 6-MAM | 20 | 40 | 100 |
| Codeine | 20 | 40 | 100 |
| Hydrocodone | 20 | 40 | 100 |
| Hydromorphone / Morphine | 20 | 40 | 100 |
| Norhydrocodone | 8 | 16 | 40 |
| Fentanyl / Norfentanyl / Alfentanil / Acetyl Fentanyl / Acetyl Norfentanyl | 2 | 4 | 10 |
| Sufentanil | 1 | 2 | 5 |
| Norsufentanil | 2 | 2 | 5 |
| Tramadol | 200 | 400 | 500 |
| Ethyl glucuronide | 4 | 8 | 20 |
| Nicotine / Cotinine | 20 | 40 | 100 |
See more easily parsable table here.
Class: Label (Name) |
Screening Test: Label (Name) |
Confirmatory Test: Label (Name) |
|---|---|---|
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) |
Final results for each substance follow these rules:
-
Positive results: If any confirmatory test for a substance analyte
(e.g., Amphetamine/
c_amp_n) is positive based on predefined thresholds, then the corresponding class-level (c_any_stim_n) and overall sample-level (c_any_specimen_n) results are also positive. -
Negative results: If all confirmatory tests for analytes in a class are negative,
then the class-level result is negative. If all classes are negative, the overall
sample-level (
c_any_specimen_n) result is negative. - Invalid results: If any confirmatory test for a substance analyte is invalid, then the corresponding class-level and overall sample-level results are also invalid.
| Level | Result Type | Example | Possible Values |
|---|---|---|---|
| Specimen | Confirmatory results (presence of any analyte) | c_any_specimen_n |
1=positive
0=negative3=invalid
|
| Class | Confirmatory results (presence of any analyte in class) | c_any_stim_n |
|
|
Analyte
|
Screening results | s_amp_n |
|
| 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 ‘c_ethanol_n’ |
1=positive0=negative3=invalid4=screen negative |
References🔗
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., … 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