The Fluorescent Treponemal Antibody (FTA) test described previously( 1) was critically appraised through participation in the Serology Evaluation and Research Assembly (SERA) Study conducted in 1956-57 ( 2 ) , and shown to produce highly sensitive and specific results. However, since completion of the SERA Study, a new chemical compound, fluorescein isothiocyanate, has been introduced (3) and is employed to produce labeled antiserums of increased potency ( 4 ) . Since fluorescein labeled antihuman globulin is the treponemal antibody detector system of the FTA test, an improvement in this reagent is reflected in an apparent increase in test. reactivity. This means that although the original I' TA test had a desirable level of reactivity, the procedure as performed( 5 ) with pressently available reagents has not been so measured. In this study, quantitation of the FTA test was undertaken to determine the present sensitivity and specificity olf the test as related to new and improved reagents and to ascertain any changes in qualitative procedure which might be employed to obtain a more satisfactolry result.Materials and methods. Test serums were obtained from the Serum Bank, USPHS Serologic Evaluation Study, and TPI Testing Service, all Venereal Disease Research ILab. Serums from the Serum Bank and TPI Testing service had been preserved by freezing at -20°C. SERA Study serums were selected for testing on basis of categories and availability. Qualitative FTA tests were performed by employing a test serum dilution of 1:s as described earlier ( 5 ) and a t dilution of 1 : 200 (FTA-200). Test serums demonstrating Reactive ( R) or Weakly Reactive ( W R ) results a t the 1 : 5 dilution were retested by preparing serial dilutions and determining a 2+ Reactive endpoint. Results obtained by the experimental qualitative procedure ( FTA-200) are expressed in terms of Nonreactive ( N ) or Reactive ( R ) . Weakly Reactive (WR I + )findings as designated for the FTA test are recorded as Nonreactive (N) in the FTA-200 procedure. Fluorescein labeled horse antihuman-globulin" was used as the treponemal antibody indicator in all tests. T h e conjugate was diluted a t 1:80 (optimal dilution for this particular lot) in phosphate buffered saline, p H 7.2 containing 2% Tween 80. Lyophilized Treponema pallidum antigen was employed for smear preparations. Two smears were prepared for each slide/test serum dilution. Of the 2 smears, the most satisfactory in terms of microscopic appearance (numbers and distributioin of T . pallida) was used folr reading and determining final reactions.
A 6-month-old boy presented with a 2-month history of developmental regression, irritability, and opisthotonic posturing. MRI demonstrated T2 hyperintensity in bilateral cerebral and peri-dentate cerebellar white matter, internal capsules, and pyramidal tracts, with hypertrophy of the intracranial optic nerves. Magnetic resonance spectroscopy (MRS) showed elevated choline peak and choline to N-acetylaspartate ratio (figure). Krabbe disease is an autosomal recessive leukodystrophy caused by deficiency of galactocerebroside -galactosidase. Accumulation of globoid cells results in optic nerve enlargement, 1 while MRS findings reflect widespread demyelination and neuronal degeneration. 2 Differential diagnosis of optic nerve enlargement includes glioma, nerve sheath meningioma, dural ectasia, and neurofibromatosis type I (NF-1). 1 Absence of hyperirritability and skin lesions can help to differentiate NF-1 and Krabbe disease.
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