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Cross-Reactivity of Chloroquine and Hydroxychloroquine With DRI Amphetamine Immunoassay

Gomila, Isabel PhD*; Quesada, Loreto PhD; López-Corominas, Victoria MD; Fernández, Julia MD§; Servera, Miguel Á. PhD; Sahuquillo, Laura PhD; Dastis, Macarena PhD**; Torrents, Albert PhD††; Barceló, Bernardino PhD*

doi: 10.1097/FTD.0000000000000382
Short Communication

Background: Chloroquine and hydroxychloroquine are medical drugs used to treat the chemoprophylaxis of malaria and a second-line anti-inflammatory drug.

Methods: We performed a study of cross-reactivity of chloroquine and hydroxychloroquine in the DRI Amphetamine Assay inspired by a case report of a self-ingestion of chloroquine after a family dispute, that involved the following: (1) an in vitro study with control samples of healthy subjects, (2) an in vivo study with samples of patients with rheumatoid arthritis, and (3) an evaluation of the cross-reactivity of chloroquine and hydroxychloroquine in 3 additional immunoassays.

Results: In the case report, the Amphetamine DRI assay resulted positive both at 1000 ng/mL cutoff (1507 and 1137 ng/mL) and at 500 ng/mL cutoff (1178 and 642 ng/mL). Chloroquine urine levels were 103,900 and 100,900 ng/mL at 5 and 9 hours after ingestion. The results with control samples showed a positive cross-reactivity of chloroquine in the DRI Amphetamine Assay (approximately 0.74% and 0.89% at cutoff of 1000 and 500 ng/mL, respectively). Hydroxychloroquine did not cross-react with the DRI Amphetamine Assay up to 1,000,000 ng/mL. In patients treated with chloroquine or hydroxychloroquine, DRI Amphetamine did not produce false-positive results. The comparative assay study showed a positive cross-reactivity of chloroquine in the Emit II Plus Amphetamines Assay with control samples.

Conclusions: Chloroquine can cause false-positive results in the DRI Amphetamine Assay when it is present at high concentrations. Hydroxychloroquine did not produce false-positive results neither in the DRI Amphetamine Assay nor in the others immunoassays evaluated.

*Clinical Toxicology Unit, Clinical Analysis Department, Hospital Universitari Son Espases, Research Institute of Health Sciences (IdISPa), Palma de Mallorca, Spain;

Research Institute of Health Sciences (IdISPa), Palma de Mallorca, Spain;

Division of Emergency, Department of Paediatrics, Hospital Universitari Son Espases, Palma de Mallorca, Spain;

§Department of Rheumatology, Hospital Universitari Son Espases, Palma de Mallorca, Spain;

Clinical Analysis Department, Hospital Universitari Son Lla[Combining Grave Accent]tzer, Palma de Mallorca, Spain;

Clinical Analysis Department, Hospital Can Misses, Ibiza, Spain;

**Division of Emergency Laboratory, Hospital Universitari de Bellvitge, Barcelona, Spain; and

††Reference Laboratory, Barcelona, Spain.

Correspondence: Bernardino, PhD, Clinical Toxicology Unit, Clinical Analysis Department, Hospital Universitari Son Espases, Research Institute of Health Sciences (IdISPa), Carretera de Valldemossa, 79, 07120 Palma de Mallorca, Balearic Islands, Spain (e-mail: bernardino.barcelo@ssib.es).

Supported in part by a grant from the Fondo de Investigación Sanitaria (PI15/00251), Instituto de Salud Carlos III, Ministerio de Educación y Ciencia, Spain.

The authors declare no conflict of interest.

Received December 07, 2016

Accepted February 06, 2017

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