The accuracy of substituted judgments in patients with terminal diagnoses.

BACKGROUND: Patients' loved ones often make end-of-life treatment decisions, but the accuracy of their substituted judgments and the factors associated with accuracy are poorly understood. OBJECTIVE: To assess the accuracy of judgments made by surrogate decision makers; ascertain the beliefs, practices, and clinical and sociodemographic factors associated with accuracy of surrogates' decisions; assess the preferences of patients for life-sustaining treatments; and compare differences in accuracy across diagnoses. DESIGN: Cross-sectional paired interviews. SETTING: Outpatient practices of three university hospitals. PATIENTS: 250 patients with terminal diagnoses of congestive heart failure, AIDS, amyotrophic lateral sclerosis, lung cancer, and chronic obstructive pulmonary disease (50 patient-surrogate pairs in each group) and 50 general medical patients and their surrogates. MEASUREMENTS: The accuracy of surrogate predictions was measured by using scales based on 10 potential treatments in each of three hypothetical clinical scenarios. RESULTS: Preferences varied according to mode of treatment and scenario. On average, surrogates made correct predictions in 66% of instances. Accuracy was better for the permanent coma scenario than for the scenarios of severe dementia or coma with a small chance of recovery (P < 0.001). In a binary logit model, the accuracy of substituted judgments was positively associated with the patient having spoken with the surrogate about end-of-life issues (odds ratio [OR], 1.9 [95% CI, 1.6 to 2.3]), the patient having private insurance (OR, 1.4 [CI, 1.1 to 1.7]), the surrogate's level of education (OR, 1.5 [CI, 1.2 to 1.9]), and the patient's level of education (OR, 1.7 [CI, 1.4 to 2.2]). Accuracy was negatively associated with the patient's belief that he or she would live longer than 10 years (OR, 0.6 [CI, 0.5 to 0.7]), surrogate experience with life-sustaining treatment (OR, 0.4 [CI, 0.3 to 0.5]), surrogate participation in religious services (OR, 0.67 [CI, 0.50 to 0.91]), and a diagnosis of heart failure (OR, 0.6 [CI, 0.5 to 0.8]). Age, ethnicity, marital status, religion, and advance directives were not associated with accuracy. CONCLUSIONS: The accuracy of substituted judgments is associated with multiple clinically apparent patient and surrogate factors. This information can help clinicians identify conditions under which substituted judgments are likely to be accurate or inaccurate and can help target populations for education designed to improve the accuracy of surrogate decision making.

Post-translational processing and Thr-206 are required for glycosylasparaginase activity.

Lysosomal glycosylasparaginase is encoded as a 36.5 kDa polypeptide that is post-translationally processed to subunits of 19.5 kDa (heavy) and 15 kDa (light). Recombinant glycosylasparaginase has been expressed in Spodoptera frugiperda insect cells enabling the precursor and processed forms to be isolated and their catalytic potential determined. Only the subunit conformation was functional indicating glycosylasparaginase is encoded as an inactive zymogen. The newly created amino terminal residue of the light subunit following maturation, Thr-206, is believed to be involved in the catalytic mechanism [1992, J. Biol. Chem. 267, 6855-6858]. Here we have constructed two amino acid substitution mutants replacing Thr-206 with Ala-206 or Ser-206 and demonstrate that both destroy enzyme activity.

Characterization of three alleles causing aspartylglycosaminuria: two from a British family and one from an American patient.

Aspartylglycosaminuria (AGU) is a lysosomal storage disease principally occurring in Finland that results from mutations in the structural gene for glycosylasparaginase (AGU). This work characterizes the inheritance of two previously reported AGU mutations in a British patient [Ikonen, Aula, Grön, Tollersrud, Halila, Manninen, Syvänen and Peltonen (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 11222-11226]. Use of the PCR determined the glycosylasparaginase cDNA sequence from both parents of the British patient and his AGU-affected brother. The father of the British AGU-affected siblings was found to be a heterozygote carrier for a C-->T point mutation which causes an Ala-->Val amino-acid substitution, while the mother was heterozygous for a 7 bp deletion that results in premature translational termination. The brother of the previously studied patient was similarly shown to be a compound heterozygote. Expression in COS-1 cells revealed the paternal Ala-->Val amino-acid substitution destroyed glycosylasparaginase catalytic activity, prevented transport of the mutant protein to the lysosome, and prevented maturation of the enzyme precursor to its native subunit structure. The Ala-->Val mutation therefore affects glycosylasparaginase in a manner similar to the Finnish AGU Cys-->Ser substitution, further supporting a linkage of glycosylasparaginase catalytic activity to its lysosomal transport and subunit processing [Fisher and Aronson (1991) J. Biol. Chem. 266, 12105-12113]. In addition, a 5 bp deletion mutation from an American patient with AGU has been characterized. The deleted sequence occurs at the beginning of the glycosylasparaginase coding sequence, resulting in an extremely truncated polypeptide. The American 5 bp deletion and the British maternal 7 bp deletion possibly decrease mRNA stability.

Structural classification of carbohydrates in glycoproteins by mass spectrometry and high-performance anion-exchange chromatography.

A general strategy has been developed for determining the structural class (oligomannose, hybrid, complex), branching types (biantennary, triantennary, etc.), and molecular microheterogeneity of N-linked oligosaccharides at specific attachment sites in glycoproteins. This methodology combines mass spectrometry and high-performance anion-exchange chromatography with pulsed amperometric detection to take advantage of their high sensitivity and the capability for analysis of complex mixtures of oligosaccharides. Glycopeptides are identified and isolated by comparative HPLC mapping of proteolytic digests of the protein prior to, and after, enzymatic release of carbohydrates. Oligosaccharides are enzymatically released from each isolated glycopeptide, and the attachment site peptide is identified by fast atom bombardment mass spectrometry (FAB-MS) of the mixture. Part of each reaction mixture is then permethylated and analyzed by FAB-MS to identify the composition and molecular heterogeneity of the carbohydrate moiety. Fragment ions in the FAB mass spectra are useful for detecting specific structural features such as polylactosamine units and bisecting N-acetylhexosamine residues, and for locating inner-core deoxyhexose residues. Methylation analysis of these fractions provides the linkages of monomers. Based on the FAB-MS and methylation analysis data, the structural classes of carbohydrates at each attachment site can be proposed. The remaining portions of released carbohydrates from specific attachment sites are preoperatively fractionated by high-performance anion-exchange chromatography, permethylated, and analyzed by FAB-MS. These analyses yield the charge state and composition of each peak in the chromatographic map, and provide semiquantitative information regarding the relative amounts of each molecular species. Analytically useful data may be obtained with as little as 10 pmol of derivatized carbohydrate, and fmol sensitivity has been achieved. The combined carbohydrate mapping and structural fingerprinting procedures are illustrated for a recombinant form of the CD4 receptor glycoprotein.