Relative reference values for clinical chemical and haematological quantities in 'healthy' elderly people

A search of the literature revealed a paucity of data on reference values for clinical chemical and haematological quantities in reasonably 'healthy' ambulant persons above 65 years of age. On the basis of 90 papers, concerning 37 different types of quantities, the median values for men and for women at 30, 50, 65, and 80 years are calculated relative to the value in men at 30 years. This transformation reduces influences of analytical and demographic factors that have caused considerable systematic differences in the original data. The reference distribution is described as regards symmetry and the change in dispersion with age. The results are given in a table and show four types of changes with age: no significant variation, a fall, an increase or a maximum somewhere between 30 and 80 years; the type of change often depends on sex.

Lactate dehydrogenase is an AU-rich element-binding protein that directly interacts with AUF1

Post-transcriptional pathways provide a major means of regulating eukaryotic gene expression. Reiterations of the AU-rich element (ARE) within the 3'-untranslated region of many cytokine and proto-oncogene mRNAs serve as signals for rapid degradation and translational repression. The identification of this cis-acting stability determinant has fueled the search for ARE-binding proteins (AUBP) that function as trans-acting factors that transduce this function. Previous work identified heterogeneous nuclear ribonucleoprotein (hnRNP) A1 as a major AUBP capable of binding the ARE of granulocyte-macrophage colony stimulating factor (GM-CSF) RNA in the context of a full-length mRNA. We report here that functional studies failed to indicate a role for hnRNP A1 in ARE-dependent mRNA turnover. In an effort to identify other functionally relevant AUBP, the major GM-CSF ARE-specific binding protein in cells lacking hnRNP A1 was purified from CB3 mouse erythroleukemia cells. Microsequencing identified this protein as the glycolytic enzyme lactate dehydrogenase (LDH) M. RNA binding by LDH was shown to occur in the NAD(+)-binding region (Rossmann fold). Polysome gradient analysis demonstrates that LDH is found in the translationally active fraction. Polysomal localization of LDH was dependent on RNA binding. Moreover, polysomal LDH exists in a complex with AUF1 and hsp-70, which has been implicated previously in the regulation of mRNA turnover. The interaction between LDH and AUF1 is direct as it can be demonstrated in vitro with purified proteins. Collectively these data implicate a role for LDH in the post-transcriptional regulation of gene expression.

Effect of age on variables relating to calcium and phosphorus metabolism in women

Lack of adequate data concerning the effect of age on biochemical variables relating to bone and mineral metabolism hampers research on age-related bone loss in women. Furthermore, to detect disease and to monitor therapy, clinical laboratories require reference values derived from an appropriate population sample. Therefore, we determined the age-specific distribution of values for serum concentrations of calcium, inorganic phosphorus, alkaline phosphatase, bone Gla protein, and parathyroid hormone; for creatinine clearance; for fasting urinary calcium:creatinine ratio; and for 24 h urinary excretion of calcium, hydroxyproline, and cyclic AMP in a population-based sample of 301 white women. From this sample, a healthy subgroup of 181 women was identified by medical record review. Age-related effects were seen in all variables except serum calcium and phosphorus. Moreover, substantial differences between the population sample and the healthy subgroup were noted in values for creatinine clearance, serum alkaline phosphatase, and 24 h urinary calcium excretion. These observations may prove useful for assessment of normality in other populations of aging white women.

Assessment of calcaemic status in geriatric hospital patients: serum ionized calcium versus albumin-adjusted total calcium

To evaluate the accuracy of total serum calcium (CaT) and albumin-adjusted total calcium (CaA) determinations in the assessment of calcaemic status in the elderly, serum ionized calcium (CaI), CaT and serum albumin (Alb) concentrations were measured in 558 geriatric hospital patients. As expected, CaT was correlated with Alb (r = 0.316, p less than 0.001) and CaI with serum pH (r = -0.351, p less than 0.001) and they were closely interrelated (r = 0.746, p less than 0.001). Various albumin-adjustment formulas from the literature decreased the correlation of CaT and CaI. Using conventional reference limits for CaT only 12% and 72% of patients with CaI above or below the reference limits for CaI, respectively, were found. This study demonstrates the low sensitivity of total and albumin-adjusted calcium in the detection of slightly or moderately abnormal calcaemic states.

Free ionised calcium--a critical survey

It is our aim to summarise and discuss procedures for the evaluation of the concentration of free ionised calcium in serum or plasma. Stress is laid upon the interrelations and relative validity of the most common algebraic expressions to appraise the calcium status. The multitude of formulae proposed in the literature are, by mathematical discussion, reduced to variations on a single theme. A second topic is the direct potentiometric measurement of free ionised calcium concentration. Finally we review the literature on the clinical utility of measuring or calculating the free ionised calcium concentration.

Differential laboratory diagnosis of hypercalcemia

It is proposed that this review will adopt the following format: establishment of hypercalcemia. This demands a discussion of the problem of normal ranges, the usage of either total calcium or ionized calcium in making this decision and where total calcium is used whether adjustment of this value for serum protein concentration should be used and if so, the formulae which have been cited to perform this. Having established hypercalcemia why is it necessary to differentiate this? This will involve reviewing those clinical situations in which differentiation of hypercalcemia has been attempted and will include an attempt to produce an up to date indication of conditions in which hypercalcemia has been described. When hypercalcemia has been established the laboratory tests which have been further used to discriminate will be divided into single tests such as N- or C- terminal parathormone, 1,25- dihydroxycholecalciferol, cyclic AMP; the combination tests which have been used including phosphate clearance, chloride vs. bicarbonate etc. proceeding to those groups which have used discriminant function to help in the decision making; dynamic testing will also be discussed particularly with reference to steroid suppression but will also include other known suppressants such as Mithramycin and Calcitonin. A final section will be included attempting to assess overall the present state of art in differentiating laboratory diagnosis of hypercalcemia and will also attempt to highlight those areas which appear to be most fruitful areas of progress in the future.

Increased absolute calcium binding to albumin in hypoalbuminaemia

The amount of calcium bound to protein was measured in 30 patients with differing diseases and varying degrees of hypoalbuminaemia. Total serum calcium increased directly with both serum albumin and ultrafilterable calcium concentrations. The estimated amount of calcium bound per gram of albumin varied inversely with the albumin concentration, decreasing from 2.1 to 1.0 mg calcium/g albumin as albumin concentration increased from 1.7 to 3.1 g/dl. Circulating parathyroid hormone (PTH) concentrations varied inversely with measured ultrafilterable calcium concentrations. The frequency of raised PTH concentrations decreased as serum albumin increased. Use of a conventional correction factor for albumin binding (0.88 mg calcium bound per gram of albumin) to calculate corrected total calcium led to major errors in estimating ultrafilterable calcium in these patients. The PTH concentrations in turn correlated with the degree of deviation between estimated and measured ultrafilterable calcium concentrations. Ionised calcium was low in seven of ten additional hypoalbuminaemic patients studied whereas correction of total calcium for albumin indicated normocalcaemia in all. Thus correction of total calcium in patients with hypoalbuminaemia by formulae which use a fixed binding ration of calcium to albumin may give an erroneous impression of normocalcaemia. The increase in calcium binding ratio during hypoalbuminaemia needs to be considered during assessment of calcium status in these patients.

Effect of albumin and free calcium concentrations on calcium binding in vitro

In vivo equilibrium dialysis studies were performed to define further the characteristics of calcium binding to bovine albumin. The concentration range for albumin (1 to 9 g/dl) as well as ultrafilterable calcium (0.5 to 2.5 mM) studied encompassed those that might be ordinarily encountered in most clinical situations. Major differences in the regressions of total calcium on ultrafilterable calcium occurred at albumin concentrations of 1, 2, and 9 g/dl but only small differences at albumin concentrations between 3, 5 and 7 g/dl. When albumin concentration was kept constant, the amount of calcium bound to albumin varied directly with ultrafilterable calcium. At any constant ultrafilterable calcium concentration albumin bound calcium varied inversely with the albumin concentrations when albumin was greater than 3 g/dl. Analysis of the data to determine association constants and molar calcium to albumin binding ratios showed that both parameters were dependent on the absolute albumin concentrations. Our results indicate that calcium binding to albumin is a complex process characterised by multiple binding sites whose affinity and binding capacity are variable. These properties suggest that correction of total serum calcium using clinical formulations with fixed calcium to albumin binding ratios may be inappropriate, particularly in hypoalbuminaemic states.

Calcium measurements in serum and plasma--total and ionized

This article will review the methods currently employed for measuring the concentrations of total and ionized calcium in serum or plasma. As far as total calcium is concerned, various techniques such as atomic absorption spectrometry, spectrophotometry, fluorometry, complexometric titration, and flame photometry will be described and compared. Particular emphasis will be given to the accuracy and precision of each technique. Possible sources of error and interfering agents will be identified and the various procedures for the taking and handling of blood samples evaluated. Inter-laboratory variation in the measurement of calcium will be studied. An assessment will be made of a new reference method for measuring total calcium in serum using isotope-dilution mass spectrometry. The usefulness of the total calcium measurement in clinical medicine will be briefly discussed. Within the last decade the refinement of spectrophotometric techniques and the improvements in ion-selective electrode technology have revolutionized the measurement of ionized calcium in serum, such that it may now be possible to replace total calcium measurements with ionized calcium measurements on a routine basis. The various techniques currently in use for measuring ionized calcium will be described and evaluated. Particular attention will be paid to the preparation of standards, the procedures for taking blood samples, and the handling of the samples prior to and during measurement. An assessment of the relative value of measuring total and ionized calcium will be presented.

A random survey of drug screening proficiency

There is little evidence of uniformity of standards of performance as influenced by technical capability and priority of concern for drug-screening proficiency. The objective of this quality-control survey was to illustrate the degree of error associated with toxicological analyses and encourage the use of controls to decrease the possibility of reporting erroneous findings.