Endogenous Digitalis-Like Factors in Human Milk

We measured the concentration of endogenous digitalis-like factors (EDLFs) in milk or colostrum of women during nursing on different days after delivery. EDLF concentrations were assayed by a solid-phase RIA involving antidigoxin antibodies and by a radioreceptor assay (RRA) involving human placenta Na+/K(+)-ATPase. The mean (SD) EDLF concentrations as measured by RIA were 35.6 (19.4) ng of digoxin equivalents per liter in milk samples (n = 37) and 61.3 (12.5) ng/L in colostrum samples (n = 5); the mean EDLF concentration as measured by RRA in milk samples (n = 11) was 573 (717) ng/L (range 0-2098). EDLF concentration in milk is greater than circulating concentrations in healthy adults but is comparable with serum concentration in the third trimester of pregnancy. In milk and serum samples (n = 8) collected at the same time, heating and (or) extracting with Sep-Pak C18 cartridges before the RIA produced significantly different EDLF values from those in untreated serum (P less than 0.001) and milk (P = 0.035). EDLF in milk appeared to be not bound or weakly bound to milk protein, as indicated by the fact that boiling did not increase the digoxin-like immunoreactivity.

Endogenous digitalis-like factors (EDLF) in obese individuals: preliminary results

We measured by RIA the serum and urinary digoxin-like immunoreactivity (EDLF) in 8 subjects with severe obesity and in 10 healthy, non-obese individuals (as a control group), to evidentiate whether circulating and urinary levels of EDLF are increased in obesity. For each individual, we measured the mean EDLF on two sera collected consecutively on two successive mornings, between 8-9 a.m. and the daily urinary EDLF excretion. Every subject collected his/her 24 hour urine in 5 different timed fractions. For each urine fraction, we measured the excretion of EDLF, electrolytes (Na and K), and creatinine. In obese people, the mean serum digoxin-like immunoreactivity (no. 8, 27.3 +/- 8.7 ng/L de) was significantly higher (unpaired t test, p = 0.0002) than in the controls (no. 10, 12.0 +/- 7.3 ng/L de), whereas control and obese subjects had superimposable 24 hour EDLF urinary excretion. Urinary excretion of EDLF significantly changed throughout the day in normals, but not in obese people. In a multiple stepwise regression analysis, urinary K+ and Na+ significantly (p less than 0.01) contributed to the regression with urinary EDLF (EDLF = 76.9 + 0.67 K+ - 0.24 Na+; R = 0.601, no. 40) in obese individuals. The in vivo kinetic and metabolic pathways of EDLF are conceivably different in obese and normal subjects. A difference in the production rate, binding to plasma proteins and/or removal mechanisms could explain the findings of higher circulating levels with normal EDLF urinary excretion in obese persons.(ABSTRACT TRUNCATED AT 250 WORDS)

Which method for quantifying "microalbuminuria" in diabetics? Comparison of several immunological methods (immunoturbidimetric assay, immunonephelometric assay, radioimmunoassay and two semiquantitative tests) for measurement of albumin in urine

We have compared the chemical and clinical characteristics of an immunonephelometric assay (INA), two immunoturbidimetric assays (ITA) and two semi-quantitative methods with those of a solid-phase radioimmunoassay (RIA) for measurement of urinary albumin (UA) concentration in 136 diabetic patients. INA and RIA had similar accuracy, and provided comparable results. However, RIA has slightly greater sensitivity than INA, which is easier and faster. Good agreement was also found between RIA and the two ITA methods, although one of these overestimated RIA values in the low-medium range (5-30 mg/l) of urinary albumin. ITA seems suitable for initial screening of albuminuria in diabetic patients but more sensitive procedures (such as RIA and INA) seem preferable for measurement of UA concentrations in the normal range. The two semi-quantitative methods showed high sensitivity but poor specificity, because of the large number of false positive results. About 50% of diabetic patients "positive" by these methods did not have microalbuminuria. The utility of these methods is questionable, because many samples from diabetic patients need to be reassayed by a more specific and sensitive assay such as the RIA, INA or ITA methods.

Does a digoxin-like substance participate in vascular and pressure control during dietary sodium changes in patients with primary aldosteronism?

To evaluate the importance of an endogenous sodium pump inhibitor in the pathogenesis of low renin human hypertension, the urinary excretion of a digoxin-like immunoreactive substance (DLIS) was measured in eight patients with primary aldosteronism (n = 5, with adenomas) during two sequential 1-week periods of low- (20 mmol/l NaCl) and high- (200 mmol/l NaCl) sodium intake. DLIS excretion increased consistently during high-sodium intake while urinary aldosterone, plasma renin activity, cortisol and adrenocorticotropic hormone did not change. Although blood pressure showed a time-course parallel to that of the urinary DLIS, the blood pressure increments were not accompanied by evidence of vasoconstriction since forearm blood flow (plethysmographic technique) increased and forearm vascular resistances were reduced. Moreover, the reactivity of forearm arterioles to local norepinephrine was unchanged during the period of low- and high-salt intake, despite the fact that an endogenous sodium pump inhibitor should, supposedly, sensitize the responses to an adrenergic agonist. Finally, forearm vasoconstrictor responses to ouabain, a pharmacological Na+,K(+)-ATPase antagonist, were potentiated during the high-salt diet, a result not expected if an increased number of sodium pumps were occupied by an endogenous inhibitor. These results provide unequivocal evidence for a modulation by salt intake of the urinary excretion of a DLIS in patients with primary aldosteronism. This substance might participate in the regulation of body fluid volume in this syndrome and possibly in other physiological conditions. However, no evidence could be found for a cause--effect relationship between blood pressure and DLIS increments during high-salt intake, at least during the short-term course of the study.

Functionally active ganglioneuroma with increased plasma and urinary catecholamines and positive iodine 131-meta-iodobenzylguanidine scintigraphy

Ganglioneuromas are usually considered not to be functionally active. Studies of their catecholamine excretory pattern and of their imaging by means of the adrenergic tracing agent 131-I-MIBG have been therefore sparse. We report on a case of secretory ganglioneuroma, as demonstrated by the increased urinary excretion of the catecholamine metabolites HVA and VMA, increased plasma dopamine and epinephrine levels, and positive 131-I-MIBG scintigraphy. We must therefore be aware that a functionally active tumor is not necessarily a neuroblastoma, and that the diagnosis should be biopsy proven.

Increased circulating concentrations of interleukin 2 receptor during rejection episodes in heart- or kidney-transplant recipients

Concentrations of interleukin 2 receptor (sIL-2R) have been suggested as a marker of rejection episodes after organ transplantation. To evaluate the analytical performance of a "sandwich-type" enzyme immunoassay method for sIL-2R and to verify whether increased concentrations of sIL-2R might be a useful marker of allograft rejection, we quantified sIL-2R in serum samples from heart- or kidney-transplant patients. The mean (+/- SD) pre-transplant value of sIL-2R (592 +/- 209 kilo-units/L) in heart-transplant patients was significantly higher (P less than 0.01) than that observed in controls (350 +/- 101 kilo-units/L). After heart transplantation, the concentrations of sIL-2R slowly decreased to baseline in successfully treated patients but increased significantly (1129 +/- 215 kilo-units/L; P less than 0.01) during acute rejection crisis. However, severe infections were also associated with a significant increase of sIL-2R, so the sIL-2R test is not specific for allograft rejection. The mean pre-transplant concentration of sIL-2R was also increased (1943 +/- 878 kilo-units/L) in 26 renal-transplant patients; after transplantation, this value returned to normal, as did that for creatinine, but persisted steadily high in five patients who experienced acute tubular necrosis. In this group of patients, the sIL-2R concentration increased by 1.5- to fourfold, both during acute rejection episodes and in clinically evident infection; thus measurement of creatinine and sIL-2R concentrations can help to distinguish between rejection, infection, and cyclosporine toxicity. In two episodes of mild cyclosporine-induced nephrotoxicity, we observed slight increases in serum creatinine (which returned to baseline when the cyclosporine dose was decreased) not associated with an increase in sIL-2R. We conclude that systematic monitoring of sIL-2R together with other biochemical and clinical markers may be useful in the management of kidney-transplant patients.

Increased circulating concentrations of interleukin 2 receptor during rejection episodes in heart- or kidney-transplant recipients

Concentrations of interleukin 2 receptor (sIL-2R) have been suggested as a marker of rejection episodes after organ transplantation. To evaluate the analytical performance of a "sandwich-type" enzyme immunoassay method for sIL-2R and to verify whether increased concentrations of sIL-2R might be a useful marker of allograft rejection, we quantified sIL-2R in serum samples from heart- or kidney-transplant patients. The mean (+/- SD) pre-transplant value of sIL-2R (592 +/- 209 kilo-units/L) in heart-transplant patients was significantly higher (P less than 0.01) than that observed in controls (350 +/- 101 kilo-units/L). After heart transplantation, the concentrations of sIL-2R slowly decreased to baseline in successfully treated patients but increased significantly (1129 +/- 215 kilo-units/L; P less than 0.01) during acute rejection crisis. However, severe infections were also associated with a significant increase of sIL-2R, so the sIL-2R test is not specific for allograft rejection. The mean pre-transplant concentration of sIL-2R was also increased (1943 +/- 878 kilo-units/L) in 26 renal-transplant patients; after transplantation, this value returned to normal, as did that for creatinine, but persisted steadily high in five patients who experienced acute tubular necrosis. In this group of patients, the sIL-2R concentration increased by 1.5- to fourfold, both during acute rejection episodes and in clinically evident infection; thus measurement of creatinine and sIL-2R concentrations can help to distinguish between rejection, infection, and cyclosporine toxicity. In two episodes of mild cyclosporine-induced nephrotoxicity, we observed slight increases in serum creatinine (which returned to baseline when the cyclosporine dose was decreased) not associated with an increase in sIL-2R. We conclude that systematic monitoring of sIL-2R together with other biochemical and clinical markers may be useful in the management of kidney-transplant patients.

Colorimetric versus radioimmunological measurement of glycated and non-glycated serum albumin after affinity chromatography

Affinity chromatography by m-aminophenylboronic acid has been proposed for routine measurement of glycated albumin. We assayed glycated and non-glycated fractions of serum albumin (HSA) eluted by affinity chromatography columns by both a specific RIA method for the human serum albumin (HSA) and by a colorimetric method. Sixteen diabetic patients presented a significantly higher percentage of glycated-HSA than 7 control subjects with both methods, and a strong correlation was found between the values obtained with the two methods. RIA was able to detect a significant concentration of glycated-HSA in all normal subjects, while the colorimetric method was not. The accuracy of separation between the glycated and non-glycated fractions of albumin was tested using [14C]glucose as tracer. When [14C]glycated-HSA purified by Sephadex G25 filtration was chromatographed using the m-aminophenylboronic acid, only 5.3% of the total 14C-radioactivity present in the solution was recovered in the bound fraction, while 44.0% was eluted in non-protein-bound fraction and 54.7% was retained in the column. Our findings confirm that affinity chromatography by m-aminophenylboronic acid can be a useful tool in the monitoring of short glycemic control of diabetic patients. Our data also indicate that the affinity chromatography with m-aminophenylboronic acid does not accurately discriminate between glycated and non-glycated fraction of HSA.

[Endodermal sinus tumor. Histological changes induced by chemotherapy]

The case of a child affected at birth sacrococcygeal teratoma is reported. Twenty-eight months following surgical resection, the tumor relapsed locally and liver metastases occurred. A biopsy of the sacrococcygeal mass was performed and histologic examination proved it to be an endodermal sinus (yolk sac) tumor. Chemotherapy consisting of etoposide and high-dose carboplatin was started. When a second operation was performed the mass had disappeared and the macroscopically involved areas of liver were removed. Histologic examination demonstrated that the complete necrosis of the tumor was partially replaced by a fibrous scar tissue. The child underwent adjuvant chemotherapy and now is in complete remission fourteen months after the last operation.

Evaluation and comparison of the analytical performances of two RIA kits for the assay of atrial natriuretic peptides (ANP)

We evaluated the analytical performance of two commercial RIA kits for the assay of plasma atrial natriuretic peptide (ANP), which use different antisera and tracers, in order to verify the most suitable RIA procedure for the assay of ANP in plasma samples. In particular, two different procedures for the purification of plasma were evaluated. The first one uses the extraction of plasma samples with Sep-Pack C18 cartridges and the second immunoextraction (C-terminal ANP-specific antibody bound to solid phase of Sepharose). The sensitivity and precision of the two RIA kits proved inadequate, being unable to provide an acceptably precise measurement of the plasma ANP concentrations in normal subjects. An improvement in precision and sensitivity was obtained by using "fresh" (or purified) preparations of the tracer and standard solutions, and by adding PEG to the B/F separation step. The direct assay (without preliminary purification) was not possible due to a serious overestimation of plasma levels due to the presence of interferences; on the other hand, the extraction step increased the imprecision and the complexity of the assay. Moreover, the extraction recovery of ANP added to plasma samples in the procedure using Sep-Pak cartridges is about 50-60%, while it was found to be almost complete (about 90%) in the immunoextraction procedure. Moreover, a comparison of the results obtained with the two RIA systems indicated that the antisera have comparable sensitivities, but quite different specificities; however, neither of the two RIA kits showed a completely satisfactory degree of sensitivity, precision and practicability.

Atrial natriuretic peptide during different pacing modes in a comparison with hemodynamic changes

The study investigates the response of atrial natriuretic peptide (ANP) to different cardiac pacing modes in comparison with hemodynamic changes. Ten patients underwent Swan-Ganz catheterization during pacemaker implant. Atrioventricular and ventricular pacing were performed consecutively at three pacing rate levels (80, 100, and 110 ppm). Blood samples were taken from the pulmonary artery for ANP determination, both basally and at the end of each pacing period. Concomitantly, mean pulmonary capillary wedge pressure (PCWP) and mean pulmonary artery pressure (PAP) were measured. Cardiac output (CO) was determined by thermodilution both basally and during the 110 ppm steps. During atrioventricular pacing, whereas no significant changes were observed for ANP, PCWP and PAP, CO increased significantly (P less than 0.0005). At the beginning of ventricular pacing hemodynamic parameters and ANP levels were comparable with those of baseline conditions. During subsequent ventricular pacing PCWP and ANP increased significantly at the 110 ppm rate step (P less than 0.05). PAP did not change significantly, whereas CO decreased in all cases (P less than 0.01). A positive correlation was observed between ANP and PCWP during ventricular (P less than 0.001), but not atrioventricular pacing. The results, while confirming the hemodynamic advantages of atrioventricular pacing, point to a major stimulation of ANP secretion during ventricular pacing. This fact, together with the observed drop in CO and the correlation between ANP and PCWP, suggest that the increase of ANP in ventricular pacing may be the expression of a compensatory mechanism to the hemodynamic disadvantages of atrioventricular asynchrony.

Exercise-induced proteinuria in well-trained athletes

We studied the rate of urinary excretion of albumin, alpha 1-microglobulin (as an indicator of the renal tubular involvement), sodium, potassium, and creatinine in the basal state (overnight urine collection) and after physical exercise (training session) in 10 professional cyclists, to verify whether protein excretion is increased even in well-trained athletes after physical effort. In addition, we wanted to understand whether the origin of exercise-induced proteinuria was glomerular, tubular, or both. Compared with the basal state (overnight collection), exercise significantly (P less than 0.01) increased the excretion rate of albumin (4.2 +/- 2.6 micrograms/min vs 18.1 +/- 10.6 micrograms/min, mean +/- SD), Na, and K, and also the urinary volume. Creatinine output was not affected by exercise. The mean (+/- SD) overnight excretion rate of albumin by athletes was quite similar to that found for 91 healthy nonathletes at rest (4.6 +/- 2.7 micrograms/min). The mean exercise-related excretion of alpha 1-microglobulin by the athletes significantly exceeded the overnight value (6.6 vs 0.3 mg/L, P = 0.037). Our study indicates that (a) albuminuria furnishes the greater contribution to the increase in exercise-induced proteinuria; (b) the exercise proteinuria is both glomerular and tubular in origin, and is reversible; (c) the enhanced protein requirement of athletes may in part be due to the recurrent excretion of proteins in the urine after physical effort.

Exercise-induced proteinuria in well-trained athletes

We studied the rate of urinary excretion of albumin, alpha 1-microglobulin (as an indicator of the renal tubular involvement), sodium, potassium, and creatinine in the basal state (overnight urine collection) and after physical exercise (training session) in 10 professional cyclists, to verify whether protein excretion is increased even in well-trained athletes after physical effort. In addition, we wanted to understand whether the origin of exercise-induced proteinuria was glomerular, tubular, or both. Compared with the basal state (overnight collection), exercise significantly (P less than 0.01) increased the excretion rate of albumin (4.2 +/- 2.6 micrograms/min vs 18.1 +/- 10.6 micrograms/min, mean +/- SD), Na, and K, and also the urinary volume. Creatinine output was not affected by exercise. The mean (+/- SD) overnight excretion rate of albumin by athletes was quite similar to that found for 91 healthy nonathletes at rest (4.6 +/- 2.7 micrograms/min). The mean exercise-related excretion of alpha 1-microglobulin by the athletes significantly exceeded the overnight value (6.6 vs 0.3 mg/L, P = 0.037). Our study indicates that (a) albuminuria furnishes the greater contribution to the increase in exercise-induced proteinuria; (b) the exercise proteinuria is both glomerular and tubular in origin, and is reversible; (c) the enhanced protein requirement of athletes may in part be due to the recurrent excretion of proteins in the urine after physical effort.

Radioreceptor assay for the measurement of endogenous digitalis-like factors using membrane particulate fraction of human placenta and 125I-digoxin: comparison with RIA method

We measured purified extracts of serum (plasma) or urine samples of newborns, pregnant women, normal adults, and uremic patients by a radioreceptor assay (RRA), which uses particulate membrane fractions from human placenta as a binding system, and 125I-digoxin as a tracer. We also measured the digoxin-like immunoreactivity by a sensitive RIA, and results were compared with those found by the RRA. Specific 125I-digoxin binding to placental receptors was competitively inhibited by purified plasma and/or urine extracts of newborns, adult subjects, pregnant women and uremic patients. A linear relationship was found between inhibition of binding and volume of plasma and urine assayed. Moreover, a significant correlation was found between the values obtained by RRA and those found by RIA (n = 17, r = 0.699, p = 0.0012). Our data confirm that increased circulating and/or urinary levels of substances with biological and immunological activity similar to cardiac glycoside drugs are present in newborns, pregnant women and uremic patients compared to healthy adult subjects. In addition, our preliminary study indicates that these endogenous factors are able to bind to the specific receptor of digitalis drugs on the placental membranes.

A pilot study of high-dose carboplatin and pulsed etoposide in the treatment of childhood solid tumors

Carboplatin was administered at 1,000 mg/m2/course in combination with etoposide at 300 mg/m2/course to 23 patients aged 5 months to 16 years. Five patients were affected by neuroblastoma, four by CNS tumors, three by Ewing's sarcoma, two by rhabdomyosarcoma, two by malignant teratoma, two by Wilms' tumor, two by head and neck carcinoma, one by hepatoblastoma, one by synovial sarcoma, and one by Langerhans-cell histiocytosis. Eleven patients were pretreated, seven of them with high-dose cisplatin. The overall response rate was 7/11 (64%) for pretreated and 10/12 (83%) for previously untreated patients. Myelosuppression was the main side effect, with anemia and thrombocytopenia more pronounced than leukopenia. Gastrointestinal toxicity and ototoxicity were very mild; nephrotoxicity and neurotoxicity other than hearing loss were not observed. In children with malignant tumors, the therapeutic activity of carboplatin at high doses, even in combination chemotherapy, deserves further studies.

High-dose carboplatin in combination with etoposide (JET regimen) for childhood brain tumors

Fourteen patients aged 1 to 15 years with medulloblastoma (six patients), low-grade astrocytoma (four patients), and high-grade astrocytoma (four patients) were treated with carboplatin and etoposide (JET regimen). Six patients had been treated previously, two of them with cisplatin at conventional doses. Carboplatin was administered at 500 mg/m2/day over 5 h on days 1 and 2, in association with pulsed etoposide at 100 mg/m2/day on days 1, 2, and 3. Courses were repeated at 3-week intervals. The disease-specific response rates were as follows: five of six with three complete responses and two partial responses for medulloblastoma; zero of four for low-grade astrocytoma; and two of four with two partial responses for high-grade astrocytoma. Myelosuppression was the main side effect: anemia (hemoglobin less than 8.0 g/dl), thrombocytopenia (less than 25,000/microliter) and leukopenia (less than 1,000 white blood cells/microliters) were noted in 19 of 54, 10 of 54, and 7 of 54 courses, respectively. Gastrointestinal toxicity was very mild, and nephro- and neurotoxicity were not observed. No audiometric abnormalities were demonstrated in seven of seven patients who had not previously received cisplatin, and preexisting audiometric abnormalities were not worsened by the administration of carboplatin in one cisplatin-pretreated patient. The combination of carboplatin and etoposide administered in this study appears to be effective and well tolerated in children with brain tumors. Further studies on a larger number of patients are needed to ascertain its real activity in childhood brain tumors.

Specific binding of cardiac glycoside drugs and endogenous digitalis-like substances to particulate membrane fractions from human placenta

We studied the characteristics of binding of cardiac glycosides to particulate membrane fractions from human placenta, to demonstrate that placental tissue is a suitable source of receptors for digitalis drugs. Moreover, we performed preliminary experiments with 125I-labeled digoxin and placental particulates to develop a radioreceptor assay for measurement of endogenous substances with activity similar to cardiac glycoside drugs (EDLS). Placental membrane fractions were incubated with [3H]ouabain (10 nmol/L) or 125I-labeled digoxin (50 pmol/L). With both ligands, binding followed a pseudo-first-order reaction kinetics and was saturable. Scatchard analysis revealed a single class of sites [for ouabain, KD = 20.2 +/- 5.8 nmol/L (mean +/- SEM), Bmax = 3.1 +/- 0.9 nmol per gram of protein; for digoxin, KD = 29.7 +/- 1.9 nmol/L, Bmax = 24.3 +/- 1.1 nmol per gram of protein]. As expected, digoxin was less potent than ouabain in displacing both tracers from digitalis drugs receptors; progesterone, cortisone, digitoxose, furosemide, bumetanide, and propranolol had no or little effect. Specific 125I-labeled digoxin binding was competitively inhibited by plasma and (or) urine extracts from newborns, adults, pregnant women, and patients with renal insufficiency. Inhibition of binding and volume of plasma and urine assayed were linearly related. These findings support the hypothesis that cardiac glycosides and EDLS can interact with the human placenta and suggest placental tissue to be a suitable source of receptors for cardiac glycosides.

Specific binding of cardiac glycoside drugs and endogenous digitalis-like substances to particulate membrane fractions from human placenta

We studied the characteristics of binding of cardiac glycosides to particulate membrane fractions from human placenta, to demonstrate that placental tissue is a suitable source of receptors for digitalis drugs. Moreover, we performed preliminary experiments with 125I-labeled digoxin and placental particulates to develop a radioreceptor assay for measurement of endogenous substances with activity similar to cardiac glycoside drugs (EDLS). Placental membrane fractions were incubated with [3H]ouabain (10 nmol/L) or 125I-labeled digoxin (50 pmol/L). With both ligands, binding followed a pseudo-first-order reaction kinetics and was saturable. Scatchard analysis revealed a single class of sites [for ouabain, KD = 20.2 +/- 5.8 nmol/L (mean +/- SEM), Bmax = 3.1 +/- 0.9 nmol per gram of protein; for digoxin, KD = 29.7 +/- 1.9 nmol/L, Bmax = 24.3 +/- 1.1 nmol per gram of protein]. As expected, digoxin was less potent than ouabain in displacing both tracers from digitalis drugs receptors; progesterone, cortisone, digitoxose, furosemide, bumetanide, and propranolol had no or little effect. Specific 125I-labeled digoxin binding was competitively inhibited by plasma and (or) urine extracts from newborns, adults, pregnant women, and patients with renal insufficiency. Inhibition of binding and volume of plasma and urine assayed were linearly related. These findings support the hypothesis that cardiac glycosides and EDLS can interact with the human placenta and suggest placental tissue to be a suitable source of receptors for cardiac glycosides.

External quality control survey for alpha-fetoprotein assay

Starting from 1984 we organized an interlaboratory quality control (QC) survey for the tumor marker AFP in which 100-150 laboratories have been involved. Seven consecutive QC cycles have been carried out during the period 1984-1988; 15-20 samples have been prepared and sent in each cycle. The 11 kits more used in the survey, which use three different immunological methods (3 kits EIA, 3 kits RIA, and 5 kits IRMA) were evaluated. Since the results of AFP assays were expressed as ng/ml of different local standards of the various kits, the participants were asked to convert their results in UI/ml of the 1st IRP 72/225 distributed by WHO. The total variability of AFP assay resulted approximately constant (19.9-24.7 CV%) during the all QC period. The validity of the consensus mean of AFP determinations obtained in the survey and assumed as reference value has been checked by recovery experiments. Regression analysis indicates that the consensus means found in these samples are in very good agreement with the added AFP. The analytical performance achieved by the most popular methods/kits, observed in the last period, are also reported.

Measurement of urinary albumin excretion (UAE) in diabetic patients: immunonephelometry versus radioimmunoassay

We have compared the chemico-clinical characteristics of an immuno-nephelometric technique (INA) with those of a solid-phase radioimmunoassay (RIA) method for the measurement of urinary albumin excretion (UAE) in diabetic patients. The UAE was evaluated in 227 diabetics; all, except 9, were Albustix-negative. The calibration of the nephelometer apparatus every time before the assay did significantly improve the accuracy and precision of the INA method. Similar values were obtained with the two methods (INA = 2.1 + 0.95 RIA, n = 227, r = 0.969) through all the ranges of albumin concentration explored. INA seems as suitable as RIA for the assay of UAE in diabetics. The two methods are comparably accurate and precise. However, RIA appears more sensitive than INA, while immunonephelometric system is easier and faster to perform (up to 200 samples can be assayed in about 1 hour, while 2-4 hours are necessary with RIA), with fewer handling steps. The INA instrumentation is automated and the reagents are more stable and less hazardous than those used in RIA. However, due to the cost of the nephelometer apparatus, the INA technique may be employed by those laboratories which have already this instrumentation or by those which will use it in the next future for the assay of other analytes in addition to albumin.