Population norms for serum ferritin.

The purpose of this study was to establish norms for the serum ferritin determination. Analyses of blood samples submitted for a panel of 29 laboratory tests in 964,325 individuals of a random population of all races in 10 centers in the United States were used. A subgroup of 59,914 ferritin values was constituted from panels that showed the values of the 28 other laboratory tests inside prescribed limits that approached the conventionally used reference ranges. The selected group was taken to be more representative of normal ferritin values than the total group, because in the former group the accompanying 28 other test parameters approached normalcy. Although both groups showed a log-normal distribution of serum ferritin values, the values of the selected group were somewhat lower than those of the total population group. The percentile distribution for men and women of different ages is portrayed. In males, the median ferritin level increased from 23 micrograms/L at ages 12 through 16 years to reach a plateau in the 120s after age 32. Values in females remained in the 30s until menopause, after which values rose to about 80 micrograms/L. The validity of these data and their clinical significance are discussed.

Population-based study of glycosylated hemoglobin, lipids, and lipoproteins in nondiabetic adults.

Glycosylated hemoglobin levels reflect glucose homeostasis over the preceding months. Many investigators have reported levels of glycosylated hemoglobin in diabetics and have noted a strong correlation of these levels with lipids and lipoproteins, but not with HDL cholesterol. We report here the first population-based study of the predominant fraction of glycosylated hemoglobin, HbA1, and its correlates in nondiabetics. In 558 euglycemic adults (fasting plasma glucose less than 140 mg/dl) aged 40 to 79 years who had no history of diabetes, HbA1 was normally distributed, was unrelated to age, and was correlated with fasting plasma glucose in men and women and with obesity in women. After adjusting for age and obesity, HbA1 was significantly correlated with total plasma cholesterol and LDL cholesterol in both sexes and with total plasma triglyceride and VLDL cholesterol in men. HDL cholesterol was not significantly associated with HbA1 in men or women. These associations are similar, although weaker, than those reported in most studies of diabetics. The finding that the association of glycosylated hemoglobin with lipids and lipoproteins extends throughout the normal range of blood sugar suggests that this association may be relevant to both the excess risk of ischemic heart disease in diabetics and in nondiabetics with higher levels of fasting plasma glucose.

Screening for carbohydrate intolerance in pregnancy: a comparison of two tests and reassessment of a common approach.

The usefulness of glycosylated hemoglobin as a prenatal screening test for carbohydrate intolerance was studied in 806 consecutive subjects by correlating glycosylated hemoglobin to 1-hour post-50 gm Glucola plasma glucose levels, 3-hour oral glucose tolerance tests, and perinatal and maternal outcomes. Sixty-seven subjects whose 1-hour post-50 gm Glucola plasma glucose levels were greater than or equal to 150 mg/100 ml underwent 3-hour oral glucose tolerance tests; 12 were diagnostic of carbohydrate intolerance. Compared to carbohydrate-tolerant control subjects, gravid patients with carbohydrate intolerance were older, more obese, had higher 1-hour post-50 gm Glucola plasma glucose and glycosylated hemoglobin levels, and infants with increased birth weight percentiles, depressed 5-minute Apgar scores, and an increased incidence of shoulder dystocia and perinatal mortality. Three of 10 carbohydrate-intolerant patients who were evaluated post partum were found to have previously undiagnosed diabetes. Division of measurements of 1-hour post-50 gm Glucola plasma glucose and glycosylated hemoglobin into normal, borderline, and suspicious groups demonstrated a reduction in discriminatory capability of glycosylated hemoglobin as compared to the 1-hour post-50 gm Glucola plasma glucose. We conclude that laboratory screening for carbohydrate intolerance should be a standard element of the prenatal evaluation; gravid patients found to have carbohydrate intolerance should be reevaluated post partum to rule out overt diabetes, and the 1-hour post-50 gm Glucola plasma glucose test is the preferred means of routine screening for carbohydrate intolerance in pregnancy.

Glycosylated hemoglobin as a screening test for carbohydrate intolerance in pregnancy.

The usefulness of glycosylated hemoglobin as a prenatal screening test for carbohydrate intolerance was studied in 806 consecutive subjects by correlating glycosylated hemoglobin to 1-hour post-50 gm Glucola plasma glucose (1 degree G) levels, and 3-hour oral glucose tolerance tests (3 degrees GTT). Sixty-seven subjects whose 1 degree G greater than or equal to 150 mg/100 ml received a 3 degrees GTT; 12 were diagnostic of carbohydrate intolerance. Compared to carbohydrate-tolerant controls, carbohydrate-intolerant gravid patients had higher 1 degree G (p less than 0.001) and glycosylated hemoglobin (p less than 0.05) levels. Linear regression analysis of 1 degree G and glycosylated hemoglobin demonstrated r = 0.35 (p less than 0.0001). Compared to the glycosylated hemoglobin test, the 1 degree G screening test has greater specificity, sensitivity, and predictive value for a positive diagnosis. Consequently, the 1 degree G is a better routine screening test for carbohydrate intolerance than is glycosylated hemoglobin.

Multilayer film analysis for glucose in 1-microL samples of plasma.

With the ultramicroanalytical system described here we can measure glucose in 1 microL of plasma or serum. The sample is placed on a dry, multilayer film element (Eastman Kodak), where a colored spot about 3.5 mm in diameter develops. The reflectance of these spots is measured with a reflectance digital matrix photometer that was conceived, designed, and constructed in our laboratory. The spot is illuminated with monochromatic light and its image is projected by a camera lens onto the photosensitive surface of a linear photodiode array containing 512 individual photodetectors. The photodetector signals are processed by a computer to obtain the reflectance and diameter of the spot. The latter is proportional to sample volume. Because the reflectance of the spot does not depend greatly on sample volume, accurate pipetting is not required. The coefficients of variation of repeatable glucose analyses were, for 400, 3000, and 5120 mg/L, 1.7, 2.3, and 2.8%, respectively. The correlation coefficient (r) between glucose analyses by our method (y) and with the Ektachem 400 (x) was 0.9918; the regression equation was y = 1.07x - 94.3 mg/L.

Reflectance digital matrix photometry.

We have designed and constructed a digital matrix photometer for quantitative measurement of reflected light of small chromophoric areas or colored spots. The areas are divided conceptually into small subunits in which the reflected light is measured. This is done through stepwise scanning with a photodiode array. The sum of the individual reflectance measurements is related to the total amount of an analyte in the spot. We have found that this technique makes possible accurate and precise quantitation of light-absorbing substances in small areas of different sizes, shapes, and internal irregularity measuring as little as 1 mm across.

The abnormal outpatient chemistry panel serum alkaline phosphatase: analysis of physician response, outcome, cost and health effectiveness.

Physician response to, as well as outcome, cost and health effectiveness of the alkaline phosphatase component of an automated chemical screening panel in the primary medical care setting were studied. Out of 118 unexpected deviations, only one new diagnosis resulted--type A viral hepatitis. Because only one new diagnosis was made during the study period, estimates are tentative; however, when compared to other tests, the alkaline phosphatase component has a low health effectiveness (0.0298 Discounted Well-Years) and a low cost-effectiveness ($85,400 per Discounted Well-Years) and does not appear to be an economic way to make new diagnoses of therapeutically responsive diseases in the primary care setting.

A long-term study of the absorption of large oral doses of folic acid.

Large daily doses of oral folic acid ranging from 25 to 1,000 mg and totalling between 1,875 and 16,000 mg per course of treatment were well tolerated without any evidence of toxic effects by four hyperuricemic men of the ages of 26, 38, 46 and 50 years. The minimum folate absorption in the gut as measured by urinary excretion ranged from 10.1 to 45.7 percent. The percentage of absorption within a give patient remained similar in successive courses and there was no evidence of saturation of the absorption process related to dose or time. The pattern of urinary excretion of folates did not indicate that appreciable fractions relative to the large folate doses were retained by the patients. Serum, erythrocyte, and urine folates returned to pretreatment levels within 120 days after treatment. These findings suggest that the folate stores of the body do not expand by orders of magnitude even when megadoses of folates are absorbed in the gut. The rise of the folate levels in erythrocytes was gradual and continuous during treatment and is best explained by postulating that incorporation of folate into red cell takes place mostly at the precursor and reticulocyte stages. The decrease of erythrocyte folate values seen 40 to 66 days after folate treatment indicates that the folate content of erythrocytes diminishes during their life span.

An instrument for digital matrix photometry.

A new instrument was conceived and designed for quantitative measurement of chromophoric areas or colored spots such as are produced in (e.g.) thin-layer chromatography. The areas to be measured are subdivided grid-like into small subunits, and the absorbance of each of these is measured. The sum of absorbances for all subunits is directly proportional to the total amount of light-absorbing substances in a spot. The absorbances of the subunits are measured with a photodetector that contains hundreds of microscopically small photodiodes, arranged in a precise geometric array. The photodiode array is interfaced with a computer via an analog-to-digital converter for numerically integrating the individual signals from each photodiode. With this analytical system, quantitation of light-absorbing substance is accurate and precise for areas of different sizes, shapes, and internal irregularity.

Effects of naloxone-HCl on cortisol levels in patients with affective disorder and normal controls.

Cortisol levels were measured before and after administration of naloxone-HCl in patients with affective disorder (n = 16) and normal control subjects (n = 8). On two consecutive days, 20 mg of naloxone-HCl or placebo was administered i.v. over 15 minutes in a double-blind crossover design. Blood samples were collected at 30, 15, and l minute(s) both before and after infusion. Cortisol rose from a mean baseline level of 14.8 microgram% to a mean peak level of 23.1 microgram% following the naloxone administration. Significant cortisol increases were found in both the 15- and 30-minute samples during the naloxone session. There were no differences between patient and normal subject samples or between diagnostic groups. A subgroup of manic patients who had responded to naloxone with a reduction of their manic behavior also had an attenuated cortisol response to naloxone. This proved to be an artifact secondary to variability in the cortisol response in these patients.

Failure of folic acid (pteroylglutamic acid) to affect hyperuricemia.

PGA administered in doses up to 1000 mg orally a day did not significantly lower the serum urate concentration nor decrease the urinary urate or total oxypurine excretion in five hyperuricemic subjects. The folate was well absorbed, as reflected by marked increases in the serum and erythrocyte folate concentrations, and up to 50% of the administered folate could be recovered in the urine. There was no evidence of clinical or laboratory toxicity at these high doses of folate. PGA is a weak inhibitor of human liver xanthine oxidase in vitro, and much of its inhibitory effect is secondary to trace contamination by pterin-6-aldehyde, a potent inhibitor of the enzyme.

Theoretical analysis of ligand-binder complex formation: partial equilibrium and incubation time.

This report presents a theoretical model of the rate at which complex formation approaches equilibrium in competitive binding systems while ligand concentration varies. Three commonly encountered systems are examined in which binder concentrations (q) are fixed at 0.5/K, 3/K and 50/K, respectively. Our analysis of the incubation time for any particular fraction of reaction completeness shows that longest incubation times occur with the lowest ligand concentrations when q = 0.5/K. However, in systems where q = 3/K and q = 50/K, the longest incubation times correspond not to lowest ligand concentrations but to those approximating the concentration of binder. It is concluded that empirical determination of minimal incubation times for these latter two assay systems should be performed with ligand and binder in approximately equal concentrations.

The weak binding reaction between folate and human serum proteins.

New evidence is presented that folic acid in serum binds with low affinity to major serum proteins. This low affinity binding is distinct from the high affinity binding by folate binding protein (FBP), a minor protein which is known to occur in serum with great quantitative variability. These conclusions are based on results obtained by equilibrium dialysis of serum containing only negligible amounts of FBP. At 4 degrees, the equilibrium value of the ratio of bound to free folate was approximately 0.81 and remained the same even wth up to 1,000 times greater than normal folic acid concentrations; however, with higher concentrations the ratio decreased progressively. These results are predicted by the laws of mass equilibria for a binding system with low ligand concentration vis-a-vis high binder concentration and low affinity between the reactants. A rough estimate of the mean affinity constant K governing this weak folate interaction with serum proteins yielded a value of 1.12 +/- 0.13 X 10(3) M-1.

Blood lead levels in San Diego policemen.

Blood lead levels were measured by atomic absorption spectrophotometry in 86 San Diego policemen to see if they would reflect the known high atmospheric lead levels in San Diego. The mean blood lead for the entire group was 27.0 microgram per dl, a level very similar to that found in the general population of other cities. Work exposure to heavy traffic, area of residence, work shift and smoking did not significantly influence blood lead. Thus, an ambient atmospheric lead load ranging from 2 to 5 microgram per cubic m does not demonstrably cause higher blood lead levels in persons exposed to such air. Surprisingly, the youngest group, 21 to 25 years, had the highest mean (32.2 microgram per dl) while the oldest, 46 to 55 years, had the lowest mean (20.9 microgram per dl), a difference statistically highly significant. However, length of work as a policeman per se did not influence blood lead levels. Exposure to other known high-risk factors (hobbies, ceramics, old dwellings) was associated with higher levels (mean 30.6 microgram per dl).

Separation of folate binding protein from human serum by DEAE-cellulose column chromatography.

On diethylaminoethyl-cellulose column chromatography, the folate binding protein in the serum of 21 patients eluted in the early effluents as a single sharply defined peak. The chromatographic behavior of the folate binder remained unchanged whether or not the serum was, before chromatography, complexed with tritium-labeled pteroylglutamic acid ([3H]PGA), dialyzed, or charcoal-adsorbed. Heating to 100 degrees C for 10 min dissociated the [3H]PGA-binder complex while destroying the folate binding property. The presence or appearance of this folate binder in increased amounts in the serum of patients with various diseases may be related to conditions of increased tissue turnover.

Relative efficacy of separation of "free" and "bound" (3',5'-3H) pteroylglutamate by charcoal coated with various materials.

We studied the effectiveness with which various charcoal preparations separate free [3H]pteroylglutamate from that complexed with milk folate binder. We tested, in various concentrations, uncoated charcoals and charcoals coated with dextrans of various molecular weights, or with albumin, hemoglubin, or polyvinylpyrrolidone with an average molecular weight of 40 000. Althouth there was some distinction between the "bound" and "free" fractions with all charcoals, those treated with dextrans of average molecular weights of 43 500 or 70 000, or with polyvinylpyrrolidone gave the best separation over a greater range of charcoal concentration. Uncoated charcoal and charcoals coated with albumin, hemoglobin, or dextran T10 (average molecular weight, 10 500) were least effective.