Ricin diagnosis

Center for Disease Control and Prevention, 2014. Ricin Diagnosis and Laboratory Guidance for Clinicians, . 

Diagnosis If signs and symptoms spelled out above are noted in large numbers of geographically clustered patients, exposure to aerosolized ricin is the suggested cause. The rapid time course of severe symptoms and death would be unusual for infectious agents. Laboratory findings are nonspecific except for specific serum ELISA (enzyme-linked immunosorbent assay). Acute and convalescent sera (plural of serum ) should be collected. 

Differential diagnosis of ricin exposure shows early inhalational ricin poisoning and will have primarily respiratory signs and symptoms, whereas ingested ricin will probably present early with gastrointestinal symptoms. 

The detection of ricin to confirm exposure is difficult, not least because the toxin is metabolized and eliminated rapidly. The most commonly used method is the enzyme-linked immunosorbant assay (ELISA) which can be applied to environmental and biological samples and allows ricin detection for up to 48 h after exposure with a detection limit of approximately 200 pg/ml (Griffiths et al, 1986 Leith et al, 1988). More recently, an ELISA that uses monoclonal antibodies with distinct specificities for ricin A and B chains has been developed (Shyu et al, 2002a) which offers high specificity but is too slow to be useful for rapid diagnosis. The same group has now developed a sensitive and rapid... 

Detection of anti-ricin antibodies could potentially aid the diagnosis of ricin poisoning in those who survive for two to three weeks. However, humoral lgM responses would likely be of short duration only and no immunological memory would be anticipated without boosting . Anti-ricin antibodies would not be detected in those dying soon after exposure. 

Biological samples from patients are generally not as useful for diagnosis of intoxications as they are for diagnosis of infectious diseases or chemical intoxications. The same is true of postmortem samples. Ricin can be identified with immunoassays in extracts of lung, liver, stomach, and intestines up to 24 hours after aerosol exposure. High doses of ricin can be identified in fixed lung tissue of aerosol-exposed laboratory animals by immunohistochemical methods. The staphylococcal enterotoxins can be detected by immunoassay in bronchial washes. Like blood and swab samples, postmortem tissue or fluid samples should be kept cold, preferably frozen, until they can be assayed. 

The diagnosis of ricin toxicosis is often based on clinical symptoms. Detection of the toxin in serum or respiratory secretimis can be done by ELISA and immu-nohistochemistry on infected tissues. Ricin is very immunogenic, thus the toxin can be detected via serology. 

---