Safety of anticoagulation in the elderly: reasons for discontinuing therapy.

We have conducted a retrospective study on the reasons for discontinuing anticoagulants in 50 patients over the age of 75 years compared with 198 adults under 75 years to determine the safety of therapy in the elderly. Venous thromboembolism and arterial embolization were the most common indications for therapy in the elderly and the median duration of therapy in all patients was 7 months (9 days-22 years). There were no deaths attributable to anticoagulants. There was no significant difference in the proportion of elderly patients who stopped treatment because of bleeding compared with 198 patients under 75 years (5/50 (10%) vs 12/198 (6.1%), P = 0.26), nor in the rate of bleeding between the two groups (5/52.5 (9.5%) treatment-years vs 12/249 (4.8%) treatment-years, P = 0.15). This complication rate does not suggest that age per se is a risk factor in the use of oral anticoagulants.

Diagnostic accuracy. The effects of multiple aetiology and the degradation of information in old age.

We propose two causes of diagnostic inaccuracy in elderly patients: multiple aetiology and the degradation of clinical information. A single clinical event in an elderly person is often the result of several small and sometimes changing aetiological factors. Multiple aetiology is particularly common in the elderly because of impairment in a number of organ systems, loss of physiological reserve, and the increased exposure to stresses. Diagnostic errors arise first because clinicians tend to look for single, large and static explanations for clinical events, and second because the errors inherent in each step in diagnosis compound when there are multiple aetiological factors. These inherent errors are also greater in old people because of difficulties in a variety of measurements. We present a numerical analysis of this which suggests that failing to make a diagnosis when the disease is present or making a diagnosis when a disease is not present is likely to occur twice as often in old as in younger patients. We suggest that these problems can be countered by being aware of the phenomenon of multiple aetiology and the diagnostic traps arising from it, and by employing the most accurate and discriminating methods when investigating elderly people. These diagnostic difficulties mean that, when they are ill and require treatment, old people need prompt access to the best of investigative and therapeutic facilities.

DNA methylation and cellular ageing.

Methylated cytosine (m5C) in DNA appears to be an important modulator of the expression of some genes. There are several lines of evidence that gradual loss of m5C is relevant to in vitro cellular ageing: m5C loss occurs during cell culture; m5C loss is detectable at an early stage of culture; m5C loss appears to be related to cell division not just duration in culture; the rate of m5C loss appears to be related to in vitro lifespan of the cell strain in question; and the total loss of m5C during an in vitro lifespan is significant by comparison with induced-changes in m5C levels which effect cell growth, or cause cell-death in culture. Progressive loss of m5C in dividing cells may thus produce the multi-step cell division "clock" which underlies the Hayflick phenomenon.

Reduced survival with increasing plasma osmolality in elderly continuing-care patients.

The results reported here are from a 2-year follow-up study of 58 elderly patients in a continuing-care unit. Most of these patients were in a hyperosmolar state at the time of entry (mean plasma osmolality 304 +/- 8 mOsmol/kg). The survival of those patients with the highest osmolality (greater than 308 mOsmol/kg) was significantly reduced (p = 0.025), with an increased mortality at 2 years (15/20 patients, p = 0.053). There was no correlation between age and plasma osmolality (r = 0.02) and the effect of osmolality on survival was independent of age. Hyperosmolality was either a marker for, or a cause of, increased mortality in this group of frail elderly patients.

Determination of 5-methylcytosine by acid hydrolysis of DNA with hydrofluoric acid.

Quantitation of 5-methylcytosine in DNA after acid hydrolysis has been inaccurate because deamination of cytosine and 5-methylcytosine occurs during the hydrolysis procedure. There is little information in the literature regarding the use of hydrofluoric acid (HF) for DNA hydrolysis and we have therefore undertaken a systematic study of this process. The deoxyribonucleotides of cytosine and 5-methylcytosine were shown not to undergo detectable levels of deamination during prolonged periods (up to 24 h) at 80 degrees C in 48% HF. Kinetic studies show that the release of purine and pyrimidine bases was complete by 4 h under these conditions. Analysis of the 5-methylcytosine content of DNA from various tissues gave levels that were very close to the values reported in the literature. This method is ideally suited for the determination of the overall cytosine methylation levels in DNA.

An evaluation of anti-insulin radioimmunodetection in patients with suspected insulinoma.

Nine patients with suspected insulinoma were scanned with iodine-131 labelled anti-insulin. The clinical diagnosis was subsequently confirmed at laparotomy in eight patients, two of whom had liver metastases. The primary insulinoma was accurately localized by anti-insulin scanning in four patients and these tumours ranged from 1 to 3 cm in diameter. Both computerized axial tomography (CT) scanning and pancreatic angiography had given false negative results in one of these patients. Hepatic metastases were correctly identified in one of two patients. No hepatic false positive reports occurred. Positive scan areas were graded as definite, probable or possible. All four of the pancreatic positive results graded as definite or probable positive were correct. Three false positive results occurred in the region of the pancreatic body, all had been graded as possible. Anti-insulin scanning failed to detect four subsequently proven insulinomata (3 mm-2 cm in diameter). Pelvic uptake of anti-insulin occurred in a patient who was found to have a para-ovarian tumour. An homogenate of this tumour also reacted with anti-insulin in a radioimmunoassay. A true negative pancreatic scan was obtained in this patient. We conclude that this technique is insufficiently accurate for routine clinical use.

The in vitro lifespan of MRC-5 cells is shortened by 5-azacytidine-induced demethylation.

The minor base 5-methylcytosine (5mC) in DNA may be important for the regulation of gene expression. Random loss of 5mC may occur during pre-replicative DNA synthesis in mortal cell strains, and thus give rise to biochemical aberrations in aging cells. 5-Azacytidine (5azaC) was used to induce loss of 5mC in DNA of human diploid fibroblasts (MRC-5) in an attempt to accelerate in vitro senescence. The 5mC content of DNA was measured by incorporation of [3H]uridine into dividing cells, hydrolysis of DNA and separation of bases by HPLC. In untreated MRC-5 cells, 5mC was 3.6% of the total cytosine (C+5mC) at population doubling (PD) 20 (28% of lifespan) and fell to 1.6% at PD 67 (97% of lifespan). A single pulse treatment with 5azaC (1 microgram/ml) induced demethylation and shortened the lifespan by 10% (6.8 PDs loss). Pulse-treated cells showed temporary growth inhibition, though they subsequently regained normal growth rate and morphology. However, uniform treatment with 0.1 microgram/ml 5azaC between PD 20 and 23 produced no immediate growth inhibition, but a 22% loss of 5mC and 25% decrement in lifespan (16.6 PDs loss). The present results indicate that 5mC levels fall during normal aging of MRC-5 cells and accelerated 5mC loss shortens the in vitro lifespan of these cells. Hypomethylation may thus be responsible for some aspects of in vitro aging.

Clinical evaluation of anti-alpha-fetoprotein radioimmunodetection.

Anti-alpha-fetoprotein (AFP) radioimmunodetection was performed in response to clinical requests in 16 patients. In two patients, assessment of a known tumour was required; the anti-AFP scans were accurate and provided useful clinical information in both cases. In the remaining 14 patients the request was for localisation of suspected recurrent tumour. Accurate information was provided in four of these patients. In this latter group, various conventional methods of investigation had failed to disclose the site of recurrence. However, of a total of 21 sites reported as positive in these 14 patients, eight proved to be false positives. Two false negative results also occurred in this group and nine could not be evaluated. Although occasionally patients were usefully scanned, improvements are necessary before consistently reliable information can be obtained using this technique.

Limiting factors in the localization of tumours with radiolabelled antibodies.

The use of radiolabelled antibodies in tumour detection is being intensely studied. Here A. R. Bradwell and colleagues discuss the use of radioimmunolocation and conclude that although many different tumour types can be localized, results at present are no better than with otherscanning techniques. Dramatic improvements will depend upon afuller understanding of tumour cell biology and the optimization of all the parameters that contribute to successful scans.

Nuclear imaging techniques with radiolabelled antibodies.

The behaviour of radioimmunolocalisation with respect to neoplasia is reviewed. The present limitations are outlined and several new approaches to improve its clinical utility are discussed.

Improved tumour localisation using indium-111 labelled antibodies.

Immunoglobulin G (IgG) antibodies to carcinoembryonic antigen (CEA) were labelled with radioactive indium (111In) or iodine (131I) and a comparison made of their value in locating CEA producing tumours. Eleven patients given 111In-anti-CEA had 31 tumours as judged by a combination of all techniques. Of these, 28 were detected by 111In-anti-CEA and 26 by conventional clinical techniques. Five of the patients also received 131I-anti-CEA. These patients had 15 tumour areas. Thirteen were detected by 111In and eight by 131I. 111In also produced a better signal to noise ratio in the scans and thereby showed lesions with greater certainty. In addition, the 111In isotope continued to accumulate in the tumour areas for considerably longer than 131I. Absorbed doses (whole body) were similar for both isotopes. The results show that antibody scanning is greatly improved by using 111In as the radiolabel in place of 131I and should allow the detection of smaller or deeper lesions.

Detection of thyroid tumours using radio-labelled anti-thyroglobulin.

IgG antibody to human thyroglobulin was labelled with 131Iodine (131I) and used to locate deposits of thyroid follicular and papillary tumours with a gamma camera. Of twelve patients studied a total of 40 tumour 'areas' were detected by a variety of clinical and radiological techniques. Sixteen of these were detected using conventional 131I uptake scans whereas 34 were positive on the antibody scans. The difficulty of assessing diffuse pulmonary lesions (3 areas) and the possibility that free 131I from labelled antibody may have contributed to the antibody scan results in six areas left 31 definite areas for scan comparison. Twenty seven (87%) areas were positive on the antibody scan, nine (29%) were positive on conventional 131I scans whilst 24 (77%) areas were detected by a combination of clinical and other radiological criteria. Five areas were positive on the antibody scan alone but there was evidence, albeit indefinite, that these areas contained tumour. Four of the 31 areas were not detected by the antibody scans. The results indicate that anti-thyroglobulin scanning is more sensitive than conventional 131I-iodide scans and may contribute to the staging and management of thyroid cancer.