title: Failure of dithiothreitol and pronase to reveal a false-positive cryptococcal antigen determination in cerebrospinal fluid.
abstract: A patient with squamous cell carcinoma of the lung and a serum rheumatoid factor (RF) of 1:1,280 had a positive cerebrospinal fluid (CSF) latex agglutination test (LAT) for cryptococcal antigen, in culture-negative, India-ink-negative CSF. Pretreatment of the sample of CSF with 2-mercaptoethanol (2-ME) ablated the antigen titer and established the presence of a false-positive LAT, whereas CSF pretreated with dithiothreitol (DTT) and pronase continued to yield a false-positive result. The differing ability of pronase, DTT, and 2-ME to eliminate interfering substances from CSF has not been previously described. Moreover, because RF is unlikely to cross the blood-brain barrier, the authors postulated that malignant disease was responsible for the patient's false-positive LAT in CSF. Hence, the authors report the case to emphasize that false-positive LAT results in CSF are unlikely to be produced by RF and to underscore the benefit of using enzymatic and sulfhydryl-reducing agents when the validity of the initial test results are in doubt. Such a procedure will optimize the chances of accurately identifying false-positive LAT results in CSF.
authors.affiliation: Department of Medicine, Jefferson Medical College, Philadelphia, Pennsylvania 19107.
authors.forename: M K
authors.initials: MK
authors.lastname: Sachs
authors.forename: C M
authors.initials: CM
authors.lastname: Huang
authors.forename: D
authors.initials: D
authors.lastname: Ost
authors.forename: D L
authors.initials: DL
authors.lastname: Jungkind
mesh_terms: D000368:Aged; D000946:Antigens, Fungal / Q000134:cerebrospinal fluid*; D002294:Carcinoma, Squamous Cell / Q000134:cerebrospinal fluid; D003453:Cryptococcosis / Q000134:cerebrospinal fluid*; D003454:Cryptococcus / Q000276:immunology / Q000302:isolation & purification*; D004229:Dithiothreitol; D005189:False Positive Reactions; D006801:Humans; D007841:Latex Fixation Tests; D008175:Lung Neoplasms / Q000134:cerebrospinal fluid; D008297:Male; D008581:Meningitis / Q000134:cerebrospinal fluid*; D008623:Mercaptoethanol / Q000494:pharmacology; D011402:Pronase; D012217:Rheumatoid Factor / Q000097:blood
chemical_list: D000946:Antigens, Fungal; D008623:Mercaptoethanol; D012217:Rheumatoid Factor; D011402:Pronase; D004229:Dithiothreitol