The Differential Agglutination (AC/HS) Test as a Diagnostic Aid in Toxoplasmic Lymphadenitis

J Clin Microbiol. 2007 Feb 21; [Epub ahead of print]

The Differential Agglutination (AC/HS) Test as a Diagnostic Aid in Toxoplasmic Lymphadenitis

Montoya JG, Berry A, Rosso F, Remington JS.

Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, Palo Alto, CA; Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA.

Lymphadenopathy (LN) is the most common clinical manifestation of acute acquired toxoplasma infection in humans. The diagnosis of toxoplasmic lymphadenitis is established by serologic methods and/or lymph node biopsy. In the United States, the AC/HS test has primarily been used in pregnant women as a component of the Toxoplasma Serological Profile (TSP), to distinguish between a recently acquired infection versus an infection acquired in the distant past. We studied the AC/HS test in patients with TL to define its usefulness in individuals presenting with LN and to determine its kinetics after the onset of LN. 109 consecutive patients (158 serum samples) diagnosed serologically and by lymph node biopsy as having TL were studied. Specific patterns in the AC/HS test were noted to be time dependent from the clinical onset of LN (COLN). Acute AC/HS patterns were observed in greater than 75% of patients who by history had developed their TL within 6 months. Acute patterns were not observed beyond month 12(th) except in a single patient in whom an acute pattern (400/800) persisted to month13th after COLN. Equivocal patterns were observed up to 36 months after COLN. Non-acute patterns were only observed in serum samples drawn at least 13 months after COLN. A non-acute pattern in an individual who has COLN of less than 12 months should suggest an etiology other than TL. In such cases, investigation for alternative causes including malignancy should be instigated.

PMID: 17314220 [PubMed - as supplied by publisher]