Cerebellar astrocytomas in elderly patients with very long preoperative histories: report of three cases.

Three patients, ages 69, 67, and 74 years, respectively, underwent surgical removal of cystic cerebellar astrocytomas. All three had past histories pointing to the existence of a cerebellar lesion for many decades prior to surgery: Patient 1 had had nystagmus on lateral gaze on the side of the tumor since early childhood; Patient 2 had had sensorineural hearing loss on the side of her neoplasm for 38 years preceding the operation; and Patient 3 was diagnosed as having a brain tumor 51 years before the operation. (He has been blind because of pressure hydrocephalus for half a century, but otherwise managed to live a productive farming and family life until he sustained a head injury in a car accident, which forced him to undergo removal of his cerebellar tumor.) The neoplasms in all three instances were found by histological examination to be low-grade astrocytomas. These cases indicate that low-grade cerebellar astrocytomas, which are well known for their characteristically long postoperative courses, may at times manifest a slow growth potential with an exceptionally long preoperative course.

Cholesterol measurements. Quality assurance and medical usefulness interrelationships.

This is a status report on cholesterol testing, using data from the College of American Pathologists Surveys program and Quality Assurance Service and the Lipid Research Clinics program. The clinical context for cholesterol testing is reviewed in order to develop a conceptual framework for analytic goals. Our analysis leads us to the following conclusions: First, the accuracy of cholesterol assays will be improved by using newly available reference material labeled by definitive methodology; this aspect of cholesterol testing is well monitored by proficiency testing. Tight goals for accuracy must await a consensus on the true value of test specimens. Second, long-term intralaboratory analytic variability, which is crucial in cholesterol testing, is well monitored by programs like the Quality Assurance Service, but not by proficiency testing. It is proposed that pathologists use realistic performance goals that incorporate a total error model and biologic variability.

Serum vitamin B12 assays. How accurate are they?

Because of clinical evidence indicated that results of radioligand assays for serum vitamin B12 did not correlate with clinical outcome, the Ligand Assay Resource Committee of the College of American Pathologists (CAP) initiated studies of biochemical specificity in the 1980 CAP survey program. In 1980, the apparent cross-reactivity of inactive cobalamin analogues was 100% in most of the vitamin B12 assays. By 1981, probably because of method changes, the apparent cross-reactivity had drastically decreased, from 100% to 10%. Recovery data confirmed adequate chemical sensitivity for true cobalamin. When evaluated against the clinical requirements for diagnosing pernicious anemia, these performance characteristics are acceptable. Radioligand assays now used by CAP survey participants yield results equivalent to those of both radioligand assays using pure intrinsic factor and to bioassays. However, because these improved assays have been in use only a short time, detailed information about their clinical utility is not yet available. Therefore, generalizations about specific clinical decision levels are not warranted at this time.

Penicillin-resistant pneumococci.

Because of reports documenting the occurrence of pneumococci resistant to penicillin, the Microbiology Resource Committee of the College of American Pathologists studied the accuracy of various Kirby-Bauer disks in identifying a pneumococcal organism known to be clinically resistant to penicillin. The only disk that showed acceptable performance was the 1-microgram oxacillin disk, using the inhibition diameter of 19 mm or less as the criterion for predicting clinical penicillin resistance. It is particularly important to understand that, at present, penicillin disks do not provide acceptable predictive accuracy.

Hormone receptors in breast cancer. Analytic accuracy of contemporary assays.

When powders of human breast carcinomas were assayed by an unselected group of laboratories, there was 90% to 98% concurrence in estrogen and progesterone receptor results. While these results demonstrate room for improvement in assay technique, it is clear that the variability due to the analysis does not exceed the variability of the clinical course and the clinical assessment of the conditions of patients with breast cancer.

Source of analytic variation in ligand assay: a study based on data from the 1976 and 1981 Basic Ligand Assay Surveys of the College of American Pathologists.

Six paired specimens distributed to laboratories in 1981 at approximately three-month intervals and four paired specimens distributed to laboratories in 1976 at intervals of three to nine months for analysis by the College of American Pathologists Survey form the basis for this study. Twelve of 37 (35%) of pool-analyte-technic combinations yielded significantly changed mean values in 1976, while 34 of 196 (17%) pool-analyte-technic combinations yielded significantly changed values in 1981. Probable instability in thyroxine and folate was demonstrated in the 1981 control pools. Precision generally continued to improve from 1976 to 1981. The poorest precision now is observed in the analysis of peptide hormones. A majority of the observed analytic variation during 1981 for most analytes relates to extralaboratory factors. Improvement in performance is largely dependent on intermanufacturer standardization of procedures and long-term maintenance of equivalence of the results of kit procedures by each manufacturer.

Precision in estrogen and progesterone receptor assays. Results of the first CAP pilot survey.

In this blind survey involving 47 unselected laboratories, 98% of participants concurred that a nominally mid-range estrogen receptor (ER) positive powder was positive; the concurrence was 91% for the progesterone receptor (PR). This precision exceeds the requirements imposed by the benefit: cost ratios which exist for the hormonal therapy of advanced breast cancer. In the same blind survey, the concurrence on nominally negative ER and PR specimens was 92% and 90%, respectively. These are also quite acceptable for the clinical context in which these tests are applied. Powders of human breast carcinoma are suitable for interlaboratory quality control. The particular lyophilized products we used were not as satisfactory.