Case diagnosis and characterization of suspected paralytic shellfish poisoning in Alaska

• Urine specimens from 11 suspected paralytic shellfish poisoning cases were analyzed.
• Four patients tested positive for exposure to saxitoxin.
• Saxitoxin was found in shellfish remnants for three of the four exposed patients.
• Dysphagia and dysarthria may be strong indicators of saxitoxin exposure.

Clinical cases of paralytic shellfish poisoning (PSP) are common in Alaska, and result from human consumption of shellfish contaminated with saxitoxin (STX) and its analogues. Diagnosis of PSP is presumptive and based on recent ingestion of shellfish and presence of manifestations consistent with symptoms of PSP; diagnosis is confirmed by detection of paralytic shellfish toxins in a clinical specimen or food sample. A clinical diagnostic analytical method using high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) was used to evaluate the diagnosis of saxitoxin-induced PSP (STX-PSP) in 11 Alaskan patients using urine specimens collected between June 2010 and November 2011. Concentrations of urinary STX were corrected for creatinine concentrations to account for dilution or concentration of urine from water intake or restriction, respectively. Of the 11 patients with suspected PSP, four patients were confirmed to have STX-PSP by urine testing (24–364 ng STX/g creatinine). Five patients had clinical manifestations of PSP though no STX was detected in their urine. Two patients were ruled out for STX-PSP based on non-detected urinary STX and the absence of clinical findings. Results revealed that dysphagia and dysarthria may be stronger indicators of PSP than paresthesia and nausea, which are commonly used to clinically diagnose patients with PSP. PSP can also occur from exposure to a number of STX congeners, such as gonyautoxins, however their presence in urine was not assessed in this investigation. In addition, meal remnants obtained from six presumptive PSP cases were analyzed using the Association of Official Analytical Chemists’ mouse bioassay. All six samples tested positive for PSP toxins. In the future, the clinical diagnostic method can be used in conjunction with the mouse bioassay or HPLC–MS/MS to assess the extent of STX-PSP in Alaska where it has been suggested that PSP is underreported.