Digoxin-like Immunoreactive Substance Research Articles

Postmortem digoxin-like immunoreactive substances (DLIS) in patients not treated with digoxin

Postmortem digoxin-like immunoreactive substances (DLIS) in patients not treated with digoxin

Analytical performance of a monoclonal digoxin assay by dry chemistry on the Vitros 950

Digoxin assay in plasma/serum samples is used for therapeutic measurements as a guide to clinical management of cardiac patients. A thin dry film multilayer monoclonal immunoassay for digoxin, Vitros, was evaluated for analytical performance. The effect of digoxin-like immunoreactive substances (DLIS) was studied assaying plasma samples taken from 100 renal disease patients, 62 hepatic disease patients and 40 pregnant women not receiving digoxin. The Vitros digoxin assay was compared with the AxSym digoxin II assay using plasma samples from 180 patients treated with digoxin. The results revealed satisfactory precision and accuracy for therapeutic drug monitoring purposes: the coefficient of variation (CV%) was lower than 5%; results for dilutions were linear in the range 0.4-3.9 microlg/L and mean analytical recovery was 105%. Measurable DLIS concentrations were observed in 29% of hepatic disease patients and in 7% of renal disease patients with apparent digoxin concentration ranging from 0.4 to 0.75 microg/L. The incidence of DLIS was comparable to that observed with AxSym digoxin II. Comparative results from patient samples gave a regression line equation: Yvitros 950=0.96XAxym +0.14, r=0.89. The data revealed a mean difference of 0.09+/-0.26 microg/L significantly greater than zero (p=0.02). We concluded that Vitros digoxin assay for precision, accuracy and extent of DLIS interference may be a good method for therapeutic drug monitoring; care needs to be taken since assay results generated by Vitros and AxSym analysers are not necessarily interchangeable.

Digoxin-like immunoreactive substance in the elderly patient and its impact on the TDx digoxin assay.

This study was undertaken to examine the impact of endogenous digoxin-like immunoreactive substance (DLIS) on the therapeutic drug monitoring of digoxin in elderly patients. Serum digoxin concentrations were detected by TDx digoxin assay in 220 patients 65 years of age and older who were not administered cardiac glycosides, spironolactone, or canrenone. The influence of clinical factors and laboratory parameters on the presence of DLIS was also evaluated. The concentration of DLIS averaged .07 ng/ml (range, 0-0.74 ng/ml), and in 25 subjects DLIS was observed over the detection limit of the assay. None of the parameters demonstrated a significant contribution to the presence of DLIS except one: continuous intravenous drip infusion therapy with a sodium-containing solution (DIV). The frequency of DLIS was significantly higher in the elderly subjects than in 121 control subjects younger than 35 years of age (p = 0.01). However, the difference became insignificant when subjects administered DIV were excluded from the analysis (p = 0.15). It was suggested that DIV may be clinically important in indicating the presence of DLIS.

Isolation and characterization of a digoxin-like immunoreactive substance from human urine by affinity chromatography

A series of observations has suggested that one or more digoxin-like immunoreactive substances (DLIS) in biological fluids is able to cross-react with the antidigoxin antibody. Whether this substance is the endogenous inhibitor of Na+/K+ ATPase has not been well established. The aim of this study was to identify and characterize DLIS from human urine. Treated urine from healthy men was run on an affinity chromatography column at a flow rate of 1 mL/min in which the ligand was an antibody (antiserum) to digoxin. Eluates from affinity chromatography were applied onto analytical reversed-phase HPLC. The active material was eluted with a linear gradient of acetonitrile (from 350 to 650 mL/L) and water. A second step in HPLC was carried out isocratically with 280 mL/L acetonitrile in water. We found a single peak showing cross-reactivity with antidigoxin antibody as measured by RIA. It showed the same retention time as that of a digoxin calibrator. This highly purified substance is able to displace [3H]ouabain from dog kidney-derived Na+/K+ ATPase, to inhibit Na+/K+ ATPase activity as measured by the 86Rb+ uptake in red blood cells and by coupled enzyme assay. Our results are consistent with the hypothesis that DLIS, as isolated by this particular digoxin antibody, is a single substance and an inhibitor of Na+/K+ ATPase.

Digoxin-like immunoreactive substance and sodium-potassium-adenosine triphosphatase inhibition in normal pregnancy: A longitudinal study

To measure the levels of digoxin-like immunoreactive substance and digitalis-like factor bioactivity as manifested by sodium-potassium-adenosine triphosphatase (ATPase) inhibition throughout pregnancy. Serum samples were collected from primigravidas in early (15 +/- 1.8 weeks), mid (26 +/- 1.2 weeks), and late (36 +/- 1.1 weeks) gestation, as well as at 6 +/- 1.1 weeks postpartum (mean +/- standard error). Digoxin-like immunoreactive substance levels were determined by radioimmunoassay and digitalis-like factor bioactivity was determined by inhibition of ATPase. Data were analyzed by means of repeated measures analysis of variance. In 41 women with normal pregnancy outcomes, levels of digoxin-like immunoreactive substance rose progressively and significantly (P < .001) throughout pregnancy and returned to normal levels postpartum. Inhibition of ATPase activity also rose significantly (P < .004), but not as dramatically, during pregnancy and remained elevated 6 weeks postpartum. Although digoxin-like immunoreactive substance levels rise in pregnancy, functional digitalis-like factor activity, as manifested by inhibition of ATPase, does not parallel this rise strictly, implying that digoxin-like immunoreactive substance receptors may be reset during normal pregnancy. The enhanced cardiac performance that occurs in normal pregnancy may be mediated in part by increased digitalis-like factor activity.

Digitoxinlike and digoxinlike immunoreactivitis in sera of patients with uremia and liver disease as measured by fluorescence polarization immunoassays: poor correlation between digitoxinlike and digoxinlike immunoreactivities.

Digoxinlike immunoreactive substances (DLIS) cross-react with antidigoxin antibodies and falsely elevante total digoxin levels. Cross-reactivity of DLIS with various immunoassays for digoxin has been extensively studied in the past. The digitoxin molecule differs from digoxin by having one extra hydroxyl group in the aglycone ring. Therefore, DLIS may also falsely elevate total digitoxin concentrations. However, in the past, limited studies have shown the presence of digitoxinlike immunoreactive substances (DTLIS) in cord blood and sera of neonates. We compared DLIS and DTLIS concentrations in sera of patients with uremia, liver disease, and hypoalbuminemia. We found measurable DLIS concentrations in 11 of 45 patients by the fluorescence polarization immunoassay (FPIA) for digoxin (range, 0.20-0.89 ng/ml digoxin equivalent). These patients did not receive any digoxin or digitoxin. Using the FPIA, we also found elevated DTLIS concentrations in 10 of these 45 patients (range, 2.88-21.24 ng/ml digitoxin equivalent). Given the narrow therapeutic range of digitoxin (15-30 ng/ml), this cross-reactivity is significant. Elevated concentrations of DTLIS in sera falsely elevated the measured concentrations of digitoxin (positive interference) when known amounts of digitoxin were added to such sera. Interestingly, we found a poor correlation between DLIS and DTLIS concentrations in sera of patients with liver disease and uremia (r = 0.58), with some patients having no measurable DLIS activity but measurable DTLIS activity and vice versa. Digoxin showed only 4-8% cross-reactivity against digitoxin antibody with a wide range of concentration. Some proposed DLIS compounds (nonesterified fatty acids, cholic acid, lysophospholipid, and DHEA-sulfate) did not show any cross-reactivity with the digitoxin assay at a concentrations much higher than the physiologic range. We conclude that DTLIS activity is present in patients with liver disease and uremia, and the correlation between DLIS activity and DTLIS activity is poor. Moreover, some proposed DLIS do not explain the DTLIS activity detected in serum.

Effects of digoxinlike immunoreactive substances and digoxin FAB antibodies on the new digoxin microparticle enzyme immunoassay.

Digoxin-like immunoreactive substance (DLIS) is known to interfere with fluorescence polarization immunoassay (FPIA) (Digoxin II, Abbott Laboratories) and falsely elevates the total digoxin concentrations. Digoxin FAB antibody (Digibind) is also known to affect digoxin results by FPIA assay. The authors studied the effects of DLIS and Digibind on a new microparticle enzyme immunoassay (MEIA) for digoxin recently introduced by Abbott Laboratories, compared with the standard FPIA method and chemiluminescence assay (ACS-digoxin, Ciba-Corning). They studied 30 volume-expanded patients (term pregnancy, liver and renal disease) for the presence of DLIS. None of these patients received digoxin. They observed measurable DLIS concentrations in 12 of 30 patients by the FPIA assay and in only 1 patient by both MEIA and ACS assays. The concentration of DLIS in that patient was 0.31 ng/ml of digoxin equivalent by the MEIA assay, 0.36 ng/ml by the ACS assay, and 1.15 ng/ml by the FPIA assay. When they supplemented serum containing digoxin with low to high concentrations of digibind (0.5, 1.0, 2.0 and 4.0, 10, and 20 micrograms/ml), and measured digoxin concentrations by FPIA, MEIA, and ACS assays, they observed lower than expected values of total digoxin. However, when they supplemented serum containing no digoxin with high concentration of digibind (5.0, 10.0 and 20.0 micrograms/ml) and supplemented protein-free ultrafiltrates with digoxin, they observed expected digoxin concentrations in the ultrafiltrates by all three assays, indicating that the ultrafiltrates are essentially free of digibind.

Monitoring Serum Free Glycoside Concentration in Elderly Patients Receiving Beta-Methyldigoxin.

The presence of endogenous digoxin-like immunoreactive substance (DLIS) has been reported in several clinical conditions. Because DLIS is absent in protein-free ultrafiltrates of sera, the monitoring of the serum free glycoside concentrations (f-SGC) rather than the total glycoside concentrations (t-SGC) seems more appropriate. We conducted the present study to obtain basic information about monitoring f-SGC in patients receiving beta-methyldigoxin (BMD), using TDx digoxin assay.The results showed that accuracy of the f-SGC detected with TDx assay is almost equal to t-SGC. Additionally, although the BMD-digoxin ratio has some influence on the evaluation of f-SGC, the impact seemed negligible if individual variance in the albumin concentration is taken into account. These findings suggest that the monitoring of f-SGC rather than t-SGC, is satisfactorily applicable in clinical situations.

Secretion of brain natriuretic peptide in patients with aneurysmal subarachnoid haemorrhage

Subarachnoid haemorrhage is commonly associated with natriuresis and hyponatraemia. One possible explanation for these features is a defect in the central regulation of renal sodium reabsorption with increased secretion of a natriuretic factor. We investigated whether excess sodium secretion in patients with subarachnoid haemorrhage is related to increased secretion of natriuretic peptides or to the presence of digoxin-like immunoreactive substances. We measured the plasma concentrations of digoxin-like immunoreactive substances (by a fluorescence polarisation immunoassay) and natriuretic peptides, aldosterone, renin, and antidiuretic hormone (by radioimmunoassay) in ten patients with aneurysmal subarachnoid haemorrhage, ten patients undergoing elective craniotomy for cerebral tumours, and 40 healthy controls of similar age and sex distribution. Samples were collected before surgery, 1 h, 4 h, and 12 h after surgery, then daily until 7 days postoperatively in the two groups of patients. All patients with subarachnoid haemorrhage, but none of the tumour patients, showed increased urine output and urinary excretion of sodium (p = 0.018 for comparison of means of curves to 7 days). The patients with subarachnoid haemorrhage had much higher plasma concentrations of brain natriuretic peptide (BNP) than controls, on admission (mean 15.1 [SE 3.8] vs 1.6 [1.0] pmol/L, p < 0.001) and throughout the study period, accompanied by lower than normal aldosterone concentrations and normal plasma concentrations of atrial and C-type natriuretic peptides (ANP, CNP). The patients with tumours had similar plasma concentrations of ANP, BNP, and CNP to the controls. We did not detect digoxin-like immunoreactive substances in either group of patients. Salt-wasting of central origin may induce hyponatraemia in patients with aneurysmal subarachnoid haemorrhage, possibly as a result of increased secretion of BNP with subsequent suppression of aldosterone synthesis.

Ｍｉｃｒｏｐａｒｔｉｃｌｅ Ｅｎｚｙｍｅ Ｉｍｍｕｎｏａｓｓａｙ（ＭＥＩＡ）法によるジゴキシン血中濃度測定の評価

The clinical usefulness of a microparticle enzyme immunoassay (MEIA) method for the determination of dogoxin in serum was investigated. The inter-and intra-assay reproducibilities of this method were 2.4 to 4.9% and 3.8 to 6.2%(C.V.%), respectively.In the determination of serum digoxin levels, MEIA well correlated with fluorescence polarization immunoassay (FPIA) (r=0.942, n=153). Cross reaction by various drugs used concomitantly with digoxin was not detected in the MEIA assay. Moreover, endogenous digoxin-like immunoreactive substance was not detected in serum from newborns (n=24) or patients with renal failure (n=42) who were not taking digoxin.

The influence of feeding regimens on endogenous digoxin‐like immunoreactive substance concentrations in infants

The aim of this study was to investigate serum digoxin-like immunoreactive substance (DLIS) levels in 60 healthy term infants when they reached 1-6 months of age with regard to feeding regimen. Group I consisted of 30 infants fed exclusively on breast milk. Groups II and III each consisted of 15 infants fed on formula and cow's milk, and on formula and cow's milk supplemented by breast milk, respectively. Mean serum DLIS concentrations were 0.03 +/- 0.05, 0.18 +/- 0.09 and 0.15 +/- 0.09 ng/ml in groups I-III, respectively. The difference between the DLIS levels in groups II and III was not significant. Serum DLIS levels of infants in groups II and III, on the other hand, were significantly higher than in group I (p < 0.05). These findings were interpreted to suggest that artificial nutrients may cause volume expansion and an increase in endogenous DLIS levels. The latter response is possibly a protective mechanism to decrease volume expansion in groups II and III.

Digoxin-like immunoreactive substance in liver failure: effect of liver transplantation and relationship to presence of hepatic encephalopathy

Objectives: To determine the contribution of liver dysfunction to the presence of digoxin-like immunoreactive substances (DLIS) in patients with liver failure on the intensive care unit (ICU); to examine the relationship between plasma DLIS levels and grade of hepatic encephalopathy (HE); and to study the effect of normalisation of liver function following successful liver transplantation (LT) on plasma DLIS levels. Design: Measurement of plasma DLIS levels, indices of liver function, and assessment of grade of HE on admission to hospital or to the ICU, and at 48 and 96 hours following LT. Setting: A teaching hospital ICU servicing the Australian National Liver Transplant Unit. Subjects: Eleven patients with stable chronic liver disease admitted for elective LT, seven patients with fulminant hepatic failure (FHF) and five patients with miscellaneous causes of liver failure with encephalopathy. Interventions: Sixteen patients underwent LT. Measurements and main results: All 23 patients had measurable level...

Digoxin-like immunoreactive substance in liver failure: effect of liver transplantation and relationship to presence of hepatic encephalopathy

Digoxin-like immunoreactive substance in liver failure: effect of liver transplantation and relationship to presence of hepatic encephalopathy

Digoxin-Like Immunoreactive Substances in Pediatric Patients Showing Cardiac Loading Findings

Digoxin-Like Immunoreactive Substances in Pediatric Patients Showing Cardiac Loading Findings

Falsely elevated serum digoxin levels secondary to endogenous digoxin-like immunoreactive substances.

Endogenous digoxin-like immunoreactive substances (DLIS) are produced by the human body and can be significantly elevated in specific clinical conditions. Commercially available digoxin assays do not have the specificity to fully distinguish DLIS from exogenous digoxin, though DLIS do not possess the same therapeutic properties as do the drug. The resultant artificial elevation of a reported digoxin level or a completely factitious level in a patient not taking the drug can have clinically significant consequences.

Vasodilatory state of decompensated cirrhosis: relation to hepatic dysfunction, ascites, and vasoactive substances.

The objective of this study was to determine the relations between the hallmark circulatory finding of decompensated cirrhosis, a reduced systemic vascular resistance (SVR), and the indices of hepatic decompensation, the accumulation of ascites, and the concentrations of various vasoactive substances. At a university-affiliated teaching hospital, eighteen hospitalized patients with cirrhosis and 18 age- and sex-matched healthy subjects were used. This was a case-control study. Measurements included cardiac dimensions and indices derived from echocardiograms and Doppler studies, abdominal ultrasound estimates of ascites, indices of hepatic function, and various serum (S) and urinary (U) substances. Results showed that cirrhotics had increased left atrial and left ventricular dimensions, left ventricular mass, heart rate, cardiac output (CO), transvalvular velocities, and a decreased SVR. SVR was related to hepatic dysfunction, as reflected by an abnormal prothrombin time ratio (r = -0.64, p = 0.006), and also related to overall severity of liver disease as estimated by the Child-Pugh score (r = -0.53, p = 0.044). Although cirrhotics with ascites generally had a reduced SVR, estimates of ascites were directly related to SVR (r = 0.57, p = 0.03) and inversely related to CO (r = -0.53, p = 0.04). Concentrations of S and U digoxin-like immunoreactive substance (DLIS) were also increased, but the concentrations of S glucagon and estradiol were not elevated. The accumulations of S and U DLIS, S glucagon, and S estradiol were all related to hepatic dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation and Comparison of the TDXII, Stratus, and OPUS Digoxin Assays

Three automated immunoassays for digoxin in serum were evaluated--Abbott TDxII, Baxter Stratus, and Behring OPUS. The accuracy and precision of the assays were assessed by weighed-in controls and an external quality control program. Coefficients of variation of all methods in serum were < or = 10% at weighed-in concentrations of digoxin of 1 and 2.5 micrograms/L. Accuracy relative to weighed-in concentrations of 1 and 2.5 micrograms/L ranged from 98 to 126% for all methods. Comparative results from patient samples showed little difference between the TDxII and Stratus and a greater difference observed between the TDxII and OPUS assays. The detection of digoxin-free samples containing digoxin-like immunoreactive substances (DLIS) in neonatal cord blood, pregnant patients, and liver and renal recipients by each assay was then assessed. The TDxII exhibited the highest incidence of DLIS. This is evident in neonatal cord blood in which 40.4% of samples tested positive. In comparison, the extent of DLIS detected by Stratus was less and OPUS exhibited no DLIS in any of the groups studied. A case study of a patient treated with anti-digoxin Fab fragments (Digibind) also was included for analysis by each method. Fourteen hours after Digibind administration, the TDxII registered a digoxin concentration of 49.5 micrograms/L compared with 3.73, 1.80, and 2.49 micrograms/L for Stratus, OPUS, and ultrafiltered TDxII methods, respectively. The results indicate that to determine the concentration of digoxin after the administration of Digiband, the OPUS or fluorescence polarization immunoassay (FPIA)-ultrafiltered samples by TDxII are the assays of choice.

Bufalin radioimmunoassays: in search of the endogenous digitalis-like substance.

The existence of a mammalian natriuretic substance similar to plant digitalis, which inhibits Na,K-ATPase, has been speculated about, but as yet no definite substance has been found. Digoxin-like immunoreactive substance (DLIS) has been reported in various clinical states including new born infants. Using bufalin (a cardioactive substance of animal origin) as antigen, four polyclonal antisera have been produced from 2 separate rabbits and characterised for cross-reactivity with 32 compounds. One antiserum showed a marked change in its cross-reactivity after resting the animal for a year. Of the endogenous substances tested, progesterone was found to be the most cross-reactive. Radioimmunoassay of foetal cord sera with different antisera, gave different levels of bufalin-like immunoactivity. However, after a novel "affinity-immunoassay" procedure, this apparent bufalin-like immunoactivity disappeared. It is concluded that bufalin-like immunoactivity in the cord blood is caused by the cross-reaction of endogenous steroids with bufalin antiserum, and the same may be true for DLIS.

The influence of tocolytic therapy on serum digoxin-like immunoreactive substance concentration.

Digoxin-like immunoreactive substance (DLIS) has been proposed to have a role in what seems to be the timely onset of labor. The relationship between the DLIS in patients with preterm labor and the success of tocolytic therapy with ritodrine and nifedipine has been studied. Using a commercially available radioimmunoassay kit, DLIS levels were determined in a total of 47 women with preterm labor and in 30 control. Tocolysis was successful in 37 of 47 women, in 20 of whom nifedipine and in 17 ritodrine was the tocolytic agent. Mean DLIS concentration was higher in patients with preterm labor. Moreover, DLIS levels were found to be decreased by successful tocolysis as could be observed from the values before initiation of tocolytic therapy and on the 3rd day of tocolysis for both nifedipine (0.268 +/- 0.198 vs. 0.220 +/- 0.210 ng/ml) and ritodrine (0.250 +/- 0.176 vs. 0.196 +/- 0.147 ng/ml; Wilcoxon test, p < 0.05).

RELEASE OF A SUBSTANCE FROM THE HUMAN PLACENTA HAVING DIGOXIN‐LIKE IMMUNOREACTIVITY

1. The human placental lobule, perfused with a constant flow (5 mL/min) of Krebs' solution after delivery at term, released into the fetal perfusate a digoxin-like substance, as measured by a fluorescence polarization immunoassay. 2. Initially the venous concentration was 360 +/- 66.7 pmol/L digoxin equivalents. This level did not change significantly during fetal vasoconstriction induced by prostaglandin F2 alpha infusion and persisted for the duration of the experiment (1.5-2 h). 3. Infusion into the fetal circulation of Fab fragments of sheep antibodies to digoxin caused vasodilatation, indicated by a fall in perfusion pressure. 4. Thus a digoxin-like immunoreactive substance, previously reported to be present in the placenta, is released into the fetal circulation and may play a role in placental control of fetal vascular tone.