Polyethylene Glycol Precipitation Test Research Articles

From stable to stable: how does stress influence the first line of immune defense in sport horses

Stressful factors, including physical exercise, can influence the body’s defense mechanisms and can be involved in the etiology and evolution of systemic diseases. The aim of this study was to investigate the influence of various stressors to which sport horses are commonly subjected on the innate immune system. For this, four experimental protocols were designed including different animals, namely: (a) resting horses subjected to everyday medium level exercise (n = 18, average age = 7 years, range: 6 to 11 years), (b) medium course transportation, where the distance of one-way trips represented 270 km (n = 8, average age = 7 years, range: 6 to 9 years), (c) a long course, with a 561 km one-way distance (n = 5, average age = 8.2, range: 7 to 11 years) and (d) pre- and post-competition investigations (n = 9, average age = 7 years, range: 6 to 11). Blood was sampled on heparine (50 UI/ml) before and after the workout or transportation. The phagocytic activity of leukocytes was measured by a carbon particle inclusion test, along with total immunoglobulin/opsonin levels (Ig) (24% Zn sulphate precipitation test) and circulating immune complexes (4.2% polyethylene glycol precipitation test). The results were statistically interpreted by use of Micrososft Excel program (Student’s t test). The various types of stress differently influenced the equine athletes. While a moderate daily exercise did not substantially influence the humoral and cellular effectors of innate immunity, transportation exerted stronger beneficial effects based on the distance to the competition site. As a fast acting antimicrobial mechanism, the phagocytosis underwent the most pronounced changes, positively influenced mainly by the short course transportation. While the transportation stress enhanced phagocytosis, the competition decreased the potential of the cells to react, without significantly influencing their numbers. The experiment suggested that management measures, such as age-tailored exercise and maternal care and diet could help in alleviating stress from stable to stable, during the competition season, thus improving animal welfare and allowing a better health forecast.

Luteinizing hormone (LH) formed a complex with an immunoglobulin G caused abnormally high levels of LH: A case report

We encountered a 30-year-old woman with remarkably elevated luteinizing hormone (LH) levels, as measured by electrochemiluminescent immunoassay (ECLIA), and no specific symptoms. We performed the following investigations: dilution linearity test, polyethylene glycol (PEG) precipitation test, immunoprecipitation test, protein G addition test, and high-performance liquid chromatography (HPLC) analysis. The linearity of patient’s serum was similar to that of a standard LH preparation, and non-specific reactions were not observed. The recovery rate of LH shown by the PEG precipitation test, immunoprecipitation test, and protein G addition test was low. Moreover, an abnormal peak in HPLC was located at a slightly larger molecular weight position than that of IgG. These results showed the presence of macro-LH, LH, and anti-LH-IgG autoantibody complex and suggested that the clearance of LH from the blood was delayed due to IgG binding, and therefore, the LH value was falsely high. We should keep the possibility of macro-LH in mind in cases of unexpectedly high LH values.

Macroprolactinemia in patients with hyperprolactinemia: an experience from a single tertiary center.

Macroprolactinemia frequently causes misdiagnosis, unnecessary investigation and inappropriate treatment in hyperprolactinemic patients. Aim of this study is to investigate the prevalence and clinical characteristics of Thai patients with macroprolactinemia. We performed a cross-sectional study in 56 hyperprolactinemic patients (51 women and 5 men) whose sera were subsequently tested for the presence of macroprolactin. Recovery of less than 40% of serum prolactin after polyethylene glycol (PEG) precipitation was indicative of macroprolactinemia. Our study revealed 19.64% (11/56) of patients with hyperprolactinemia were found to have a preponderance of macroprolactin. All patients with macroprolactinemia were women, of which eight of them were initially diagnosed as idiopathic hyperprolactinemia and mistreated with dopamine agonist medications. Interestingly, neuroradiological abnormalities were reported in three patients with macroprolactinemia, 2 cases with prolactinoma and one case with stalk effect hyperprolactinemia. In conclusion, nearly one-fifth of our patients with hyperprolactinemia have macroprolactinemia. This finding suggests that the diagnostic algorithm of all patients with hyperprolactinemia should include the PEG precipitation test as the initial step.Domain: Endocrinology

Makroamilazemija kao razlog hiperamilazemije u klinički nejasnim stanjima - prikaz slučaja

Macroamylasemia is a rare condition characterized by elevated serum amylase levels due to the existence of macromolecules - complex amylase that cannot be secreted normally by the kidneys due to their size. It is a benign condition that is usually free of marked clinical symptoms and signs. The prevalence of macroamylasemia in the population is between 1 and 2%. The main clinical significance of macromylasemia is that it is often a diagnostic problem because it requires differentiation of this condition from other causes of hyperamylasemia. Therefore, it is rational to avoid unnecessary diagnostics and treatment, which burden both the patient and the health system. Macromalasemia as a diagnosis should be considered in any patient with elevated serum amylase activity in whom serum lipase and urine amylase levels are normal. Laboratory confirmation of the diagnosis of amylasemia rests on tests: electrophoresis or polyethylene glycol precipitation test. This paper presents a patient who has been routinely treated clinically due to non-specific gastrointestinal problems. During laboratory treatment, the patient's serum was found to have elevated amylase values. Additional diagnostics did not identify organic pancreatic diseases or other diseases that may be related to hyperamylasemia, and by calculating the ratio of renal amylase clearance to creatinine clearance of less than 1%, we conclude that it is most likely a macroamylasemia. Specific treatment was not required. The patient comes for a check-up once every 6 months.

Falso incremento de la hormona estimulante del tiroides asociado a la presencia de macro-TSH

Woman showing an important increase of serum TSH (62.2 mU/L) with thyroid hormones within the reference interval. The patient was clinically euthyroid and without goitre. Investigations were carried out to determine the origin of the unexpected high TSH. Polyethylene glycol precipitation test showed low TSH recovery (1%), indicating the presence of large molecules that could interfere with the measurement. The serum sample was fractionated by gel filtration chromatography and the presence of a macro-TSH form was confirmed, an immunoreactive but biologically inactive TSH-Immunoglobulin G autoantibody complex. Its detection is important to avoid a misleading interpretation of the TSH concentration.

Falsely Elevated Thyroid-Stimulating Hormone (TSH) Level Due to Macro-TSH

We encountered a 60-year-old woman with remarkably elevated thyroid-stimulating hormone (TSH) level as measured by electrochemiluminescent immunoassay (ECLIA), but with no specific symptoms, and with normal levels of free T3 and free T4. We performed the following investigations: polyethylene glycol (PEG) precipitation test, human antimouse IgG antibody (HAMA) interference test, and 3 additional TSH measurements by chemiluminescent immunoassay (CLIA). We then performed 2 gel filtration chromatography (GFC) procedures; one was at pH 7.2, and the other was at pH 3.0. Although the recovery of TSH shown by the PEG precipitation test was 4% which was extremely low, no HAMA interference was observed. Moreover, 3 CLIA instruments also showed various high values. The first GFC showed that the main peak of TSH immunoreactivity by ECLIA was located at a slightly larger molecular weight position than that of IgG. By the second GFC, the sample from the peak fraction of the first GFC showed that the TSH peak disappeared completely at the previous retention time but newly appeared at the same retention time as the TSH monomer. Protein G-Agarose gel removed the majority of the TSH complex. In conclusion, the majority of TSH in her serum was macro-TSH; TSH and anti- TSH IgG autoantibody complex. We should keep the possibility of macro-TSH in mind in cases with unexpectedly high TSH values, especially in autoimmune thyroidal disorders.

A study of the cellular and humoral immune response in patients with myelofibrosis.

There was evidence of impaired cellular immunity in 10 patients with myelofibrosis. In-vitro lymphocyte transformation with phytohaemagglutin, concanavalin A, and dinitrochlorobenzene skin reaction were diminished. Signs of impaired humoral activity were also found, the primary response to alpha-Helix pomatia haemocyanin being impaired, particularly in the immunoglobulin-A class. Moreover three patients had a benign paraproteinaemia. Immunecomplexes (IC) could be demonstrated with various test systems. The indirect granulocyte phagocytosis test was positive in 50%, the C1q-binding in 70% and the polyethylene glycol precipitation test in 50%. In most patients complement levels were normal, although the patient with the most advanced disease had low C3A, C3 and C4 levels accompanied by high levels of IC. No correlation could be shown between impaired immune response or levels of IC when they were related to spleen diameter or degree of anaemia. Some relation however existed between disturbed immune response and IC when they were related to time elapsed since diagnosis. It is suggested that the impaired immune response is the result of primary bone marrow disease and that the presence of IC may reflect the extent of fibrosis.

False-positive polyethylene glycol precipitation tests for macroprolactin due to increased serum globulins

The polyethylene glycol (PEG) precipitation test is widely used to detect hyperprolactinaemia caused by macroprolactin. We report two cases of hyperprolactinaemia in which a low recovery of serum prolactin (PRL) after PEG precipitation indicated the presence of macroprolactin, but no macroprolactin was detected by gel filtration chromatography (GFC). Both cases had elevated concentrations of serum globulin (IgG myeloma and polyclonal hypergammaglobulinaemia due to human immunodeficiency virus [HIV] infection), which prompted us to investigate further the effect of serum globulin on the specificity of the PEG precipitation procedure. The effect of increasing concentrations of gamma globulin on the precipitation of PRL by PEG was studied by adding purified human gamma globulin to serum. Ten samples from HIV-infected patients, which showed a low recovery of PRL after PEG precipitation (<60%) were studied with GFC. Addition of gamma globulin decreased the recovery of PRL following precipitation with PEG and gamma globulin concentrations correlated inversely with PRL concentrations (r = 0.9429, P < 0.0167) and percentage recovery of PRL (r = -1.000, P < 0.005). Only one out of 10 samples from HIV-infected patients with PRL recoveries of <60% following PEG precipitation showed a substantial macroprolactin component on GFC. Monomeric PRL is co-precipitated with serum globulins by PEG. Increased serum globulin concentrations can increase the amount of monomeric PRL precipitated by PEG giving a false estimate of the monomeric PRL and the erroneous impression that macroprolactin is present. The results of the PEG precipitation test should be interpreted with caution in patients with elevated serum globulin concentrations.

Polyethylene glycol precipitation: proceed with care

Two articles in this volume of the Annals demonstrate the utility of polyethylene glycol (PEG) precipitation for the detection of serum macro-analytes. In these cases, elevated aspartate aminotransferase (AST) activity was due to the enzyme being sequestered in serum as a high molecular mass (macro) enzyme complex rather than as a result of increased AST release by damaged tissue. PEG precipitation is now widely used in UK laboratories to detect elevated serum prolactin concentration due to macroprolactin and familiarity with the technique and ready availability of the reagent may encourage laboratories to use this approach for the investigation of other macro-analytes which can cause similar diagnostic confusion and patient mismanagement. PEG precipitation undoubtedly has the potential for wider routine application and has been used to study interference from macro-analytes or immunoglobulins in assays for various cytokines, C-terminal telopeptide of type I collagen, cardiac troponin I, a-fetoprotein, C-reactive protein, IgA, IgM, insulin, thyroid-stimulating hormone (TSH), parathyroid hormone, prolactin, luteinizing hormone, follicle-stimulating hormone (FSH) growth hormone, total triiodothyronine, creatine kinase (CK), amylase, alkaline phosphatase (ALP), AST, alanine aminotransferase (ALT) lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT). However, the PEG precipitation test has limitations and the characteristics of the technique, particularly the specificity and the capacity of PEG to interfere in some assays, must be appreciated if the test is to be applied appropriately and the results interpreted correctly. PEG precipitation is a crude and non-specific technique, which separates proteins by virtue of their solubility. PEG acts as an inert solvent sponge, reducing solvent availability. With increasing concentration of PEG the effective protein concentration is increased until solubility is exceeded and precipitation occurs. When applied to serum PEG precipitation is relatively specific for Igs and Ig complexes. However, it should be noted that precipitation of IgA is only partial and a preliminary report indicates that the rare cases of macroprolactinaemia with an IgA macroprolactin may be missed. Macroamylase is predominantly an IgA complex but similar problems of incomplete precipitation by PEG have not been reported. Unfortunately, PEG precipitation is not entirely specific for Igs and Ig complexes in serum. When used to detect macro-analytes a proportion of the free analyte is invariably precipitated by PEG and this varies considerably between analytes and also for any given analyte. For example, the upper limit of the reference range for PEG precipitated activity (PPA) of seven commonly measured serum enzymes varies from 36% (ALP) to 76% (ALT) and the reference range for PPA for LDH is 12–70%. While the precipitation of free, monomeric prolactin has been shown to be influenced by the concentration of serum gamma globulins this does not account for all of the variability for this analyte and other, as yet unknown factors must be present. Attempts to optimize the concentration of PEG used to selectively precipitate macro-analytes are often thwarted by proportionate effects on the solubility of the uncomplexed analyte as demonstrated for CK in serum. While PEG is relatively inert and the precipitated protein can be re-dissolved for further study, a further limitation of the method is that PEG can interfere with some immunoassays. All of the effects discussed above necessitate the determination of appropriate analyte and method specific reference ranges and the examination of a wide range of serum samples to exclude potential matrix effects. Furthermore, as the elevation in activity or concentration caused by macro-analytes is most frequently modest the cut-offs used with PEG precipitation to detect such cases inevitably sacrifice specificity for sensitivity and confirmatory tests are required. These are usually more complex and expensive and may not be readily available in the routine laboratory. When PEG precipitation has been applied to the detection of macroenzymes, results have usually been reported as the percentage of enzyme activity precipitated, which is directly related to the proportion of macroenzyme present. When applied to detection of macro-hormones, particularly macroprolactin, the results have largely been reported as percentage recovery of hormone, which is inversely related to the proportion of macro-hormone present. Recently, it has been argued that the priority for the laboratory should be to determine whether the bioactive monomeric prolactin is elevated rather than simply detect the presence of macroprolactin and it has been demonstrated that interpretation of results in terms of percentage recovery can be misleading when macroprolactin is present and the monomeric prolactin concentration is elevated. It has been proposed that the prolactin concentration after PEG precipitation be taken as a measure of monomeric prolactin

Prevalence of increased serum creatine kinase activity due to macro-creatine kinase and experience of screening programmes in district general hospitals

Macro creatine kinase type 1 (MCK1) may be the cause of elevated total serum CK activity, which can lead to diagnostic confusion. There is evidence that this problem is poorly recognized perhaps due to a lack of information on its prevalence. Precipitation with polyethylene glycol (PEG) has been described for the detection of MCK1 but has not been fully evaluated. We introduced a screening programme to detect elevated serum total CK due to MCK1 and determine the prevalence of this problem using PEG precipitation with confirmation by gel filtration chromatography (GFC). The results were compared with those from a laboratory which selected samples for further investigation during the clinical validation process. We also studied characteristics of the PEG precipitation test including sensitivity and specificity when compared with GFC. Over 2 years we screened 368 patients. In 17 cases the proportion of CK activity precipitated by PEG was relatively high and the presence of MCK1 was confirmed in seven by GFC. In a second laboratory, over a period of 5 years, 11 samples were selected during the clinical validation process for further study and MCK1 was the cause of the elevated CK activity in six cases. PEG precipitates a proportion of normal, uncomplexed CK and this is increased by increasing serum globulin concentration and by higher concentrations of PEG. The prevalence of elevated serum CK activity due to MCK1 was approximately 2%. Laboratories should consider introducing a systematic screening programme based on PEG precipitation.

Patients with macroprolactinaemia: clinical and radiological features

Macroprolactinaemia may represent a relevant cause of misdiagnosis, unnecessary investigation and inappropriate treatment. The aim of this study was to investigate the clinical and neuroradiological characteristics of patients with and without macroprolactinaemia and to evaluate the impact of macroprolactin determination on the diagnostic work-up of hyperprolactinaemic patients. Retrospective analysis in 135 consecutive hyperprolactinaemic patients (111 women and 24 men; mean age 37 +/- 11.6 years) whose archived sera were subsequently tested for macroprolactin. Recoveries </= 40% after polyethylene glycol precipitation were indicative of macroprolactinaemia. Macroprolactin, entirely explaining biochemical hyperprolactinaemia, was found in 42.2% of patients, a third of whom presented with signs and symptoms of hyperprolactinaemia. Determination of macroprolactin changed the initial diagnosis in a consistent proportion of patients. In particular, idiopathic hyperprolactinaemia, initially diagnosed in 41 patients, was then excluded in 28 of them. Diagnosis of prolactin-secreting pituitary microadenoma shifted to non-secreting pituitary microadenoma in 10 of 49 patients, while in all patients with prolactin-secreting pituitary macroadenoma or hyperprolactinaemia due to stalk deafferentation the presence of macroprolactin was excluded and the initial diagnosis confirmed. Finally, macroprolactin was present in the majority of patients with magnetic resonance imaging (MRI) scans suggestive for primary empty sella (4 of 5 women) or pituitary hyperplasia (12 of 17 women, 3 of 3 men). Collectively, about half of subjects with macroprolactinaemia showed variable MRI abnormalities. The presence of macroprolactin was a relevant cause of misdiagnosis in patients with hyperprolactinaemia. However, due to the unexpected high frequency of pituitary abnormalities observed in the present series, we suggest that the diagnostic algorithm of hyperprolactinaemic states should include both polyethylene glycol precipitation test and MRI imaging.

Prevalence of Macroprolactin Detected by Elecsys® 2010

Background: Macroprolactin or big-big PRL is, usually, a complex of little prolactin (PRL) with anti-PRL autoantibody. There are some patients with hyperprolactinemia showing a high proportion of serum macroprolactin. However, its clinical significance is not clear. Immunoassays used to determine PRL differ in their ability to detect macroprolactin. Moreover, in recent years, PRL assays have changed from isotopic methods (radioimmunoassays and immunoradiometric assays) to non-isotopic automated immunoassays. The effect of macroprolactin on currently used methods is often unknown. The aim of this work was to study the different reactivity of macroprolactin in two immunoassays systems, Elecsys 2010 and ACS Centaur, and to assess the clinical repercussion of this condition. Methods: We studied retrospectively 956 consecutive routine patients. Samples with a PRL value >636 mIU/l (211 samples) were subjected to the polyethylene glycol (PEG) precipitation test to detect macroprolactin, and 2 of them also to gel filtration chromatography for further confirmation. PRL was measured by Elecsys 2010 and, alternatively, by ACS Centaur. Results: By Elecsys 2010, macroprolactin was detected in 19 patients (9%). After removing macroprolactin, PRL levels were within the normal range in every case but one. When original sera from patients with macroprolactin were processed with ACS Centaur. PRL levels were normal or only marginally elevated. The correlation of PRL values in samples with and without macroprolactin assayed by both systems was 0.64 and 0.98, respectively. Conclusions: Nearly 9% of hyperprolactinemic patients detected by Elecsys 2010 may have macroprolactin, but the detection rate obtained using ACS Centaur is much lower. As macroprolactin seems to have minimal clinical relevance, it would be important that the users of PRL assays be aware to what extent macroprolactin interferes with their assays, and have available a validated method, such as the PEG precipitation test, to confirm the presence of macroprolactin.

Macroprolactinaemia: validation and application of the polyethylene glycol precipitation test and clinical characterization of the condition.

The clinical characteristics and natural history of macroprolactinaemia are yet to be fully established and there is currently no widely accepted simple in vitro test for routine identification of the condition. This study was designed to further validate the polyethylene glycol (PEG) precipitation test with assessment of percentage prolactin recovery (%R), for the detection of macroprolactinaemia and clinically characterize cases identified using the test. Analytical validation and application of the PEG precipitation test for diagnosis of macroprolactinaemia and a retrospective case-notes review of some of the patients identified with the condition. Sera from 188 patients with elevated serum prolactin (PRL) concentrations were screened for macroprolactinaemia. Seventeen of the patients who were under follow-up at the local teaching hospital and were identified to have macroprolactinaemia were systematically characterized clinically. Prolactin was measured in sera, fractions from gel filtration chromatography and supernatant obtained after PEG precipitation, by the DELFIA fluoroimmunoassay. CLINICAL ENDPOINTS: Initial serum PRL and symptoms and their response to dopamine agonist therapy; imaging of the pituitary gland; serum PRL and symptoms after cessation of dopamine agonist therapy; course of serum PRL and symptoms without dopamine agonist therapy. The within-batch coefficient of variation (CV) of the PEG precipitation test ranged between 2.8 and 7.3% while the between-batch CV ranged between 3.4 and 9.7%. Intra-individual variability up to five months was 9.9%. A prolactin recovery </= 40% was indicative of macroprolactinaemia, while the condition was unlikely to be present at values > 50%. The prevalence of macroprolactinaemia was 15% without sex difference. Clinical characterization of 17 patients showed modest initial serum PRL concentrations and there was imaging evidence of a coexisting pituitary adenoma in three of them. Dopamine agonist therapy resulted in substantial falls in serum PRL and this was associated with improvement or resolution of symptoms in some patients. Stoppage of dopamine agonist resulted in rebound hyperprolactinaemia in all cases. Spontaneous improvement in symptoms occurred in three patients but hyperprolactinaemia persisted in all those who were not on treatment. The PEG precipitation test with assessment of 'free' prolactin has been shown to be reproducible and sensitive for the detection of macroprolactinaemia. Many of the patients who had macroprolactinaemia presented with at least one symptom of the hyperprolactinaemic syndrome. Dopaminergic therapy may influence the course of both serum PRL and symptoms in some of these patients.

Complement activation during an active cytomegalovirus infection after renal transplantation: Due to circulating immune complexes or alternative pathway activation?

In 32 patients with a renal allograft, serial determinations after transplantation were made of C3d, the stable conversion product of the complement factor C3, as well as serial measurements of the anaphylatoxin C3a des arg. Furthermore, serial determinations were made on the presence of circulating immune complexes using three different assays (C1q binding assay, polyethylene glycol precipitation test, and indirect granulocyte phagocytosis test). Twenty patients were studied during an active cytomegalovirus (CMV) infection, and 12 patients were studied during allograft rejection or during stable phase after renal transplantation. In 12 patients with a CMV infection serial measurements were made of AP50 (alternative pathway of complement). During an active CMV infection elevated C3d as well as elevated C3a des arg levels were found and not in the control group ( P < 0.01). In 8 out of the 12 patients tested, with CMV infection, a decreased hemolytic activity of the alternative pathway (AP50) was found, together with the elevated levels of C3d and C3a des arg. Serum C4 levels were normal or high during CMV infection. Furthermore, circulating immune complexes were found to be positive in 15 out of the 20 patients with a CMV infection (both primary and secondary infections), and in 2 out of 12 patients of the control group. The complement activation found in the CMV group was not related to the presence of circulating immune complex-like material, since complement activation was present in advance of the appearance of the immune complexes, suggesting that complement activation was not due to classical pathway activation by those complexes. We conclude that our data are consistent with complement activation and the formation of biologically active peptides like C3a des arg in patients with an active CMV infection. The decreased hemolytic activity of the alternative pathway (AP50) together with the normal or high C4 levels suggest involvement of the alternative pathway, although further studies of the alternative pathway of C are warranted to confirm this hypothesis.

Clinical importance of circulating immune complexes in human acute lymphoblastic leukemia.

A total of 122 sera from acute lymphoblastic leukemia (ALL) patients were analyzed for circulating immune complexes (CIC) by two methods: the 125I-Clq binding assay and the polyethylene glycol precipitation test (PEG). The results were correlated with induction, remission and relapse stages of the disease. Using the first method the levels of CIC in induction were 15.18 +/- 9.15, with 19/29 positive cases (65.50%), P less than 0.001 compared with controls. In the remission phase the levels were 9.02 +/- 5.62, 11/45 (24.49%) nonsignificant P value, and in relapse they were 16.14 +/- 11.17 28/48 (58.33%) P less than 0.001. The PEG precipitation test results were: 0.33 +/- 0.10, 8/22 (36.36%); 0.24 +/- 0.11, 10/48 (20.83%) and 0.28 +/- 0.10, 6/28 (21.42%), respectively. Thus the values of CIC as measured by PEG in the three clinical of phases ALL did not differ significantly from controls. This contrasts with results obtained by the radioiodinated C1q binding assay, where the incidence of positive values was significantly higher in induction and in relapse and lower in the remission phase. These observations were extended in sequential vertical studies performed in a group of patients. These results suggest that raised CIC detected by the 125I-C1q method may reflect a progressive state in ALL and that quantitation of these immune complexes may provide an adequate biochemical marker for prognosis.

Screening for macroamylase in a community hospital.

We evaluated the polyethylene glycol precipitation test (Gastroenterology 83: 378-382, 1982), looking for macroamylase in the serum of 66 patients whose values for serum amylase were above normal. Three patients (4.5%) were identified by this method as having macroamylase , and this was confirmed by gel-filtration chromatography and electrophoresis. We find this to be the test of choice as a screening procedure for macroamylasemia because of its speed, simplicity, and apparent reliability. Diagnosis of macroamylasemia is important in preventing needless treatment and investigation for pancreatitis.

Circulating Immune Complexes in Healthy Persons

The prevalence of circulating immune complexes (CIC) and C4 and C3 activation products (C4 and C3 A.P.) was investigated in sera from 106 blood donors, 100 hospital staff-members, 63 patients with rheumatoid arthritis and active synovitis, and in 25 hospital staff-members who had monthly tests performed during one year. CIC were detected by means of a complement consumption test and a polyethylene glycol precipitation test. C4 and C3 A.P. were demonstrated by means of crossed immunoelectrophoresis. No significant differences in the prevalence of CIC were found between blood donors and hospital staff-members (3 and 9%, respectively) and no age and sex differences were observed. In the longitudinal study of hospital staff-members, a significantly increased incidence of CIC was found during the winter months. CIC were found in 86% of the patients with rheumatoid arthritis. C4 and C3 A.P. were found significantly more often in sera with than without CIC. The significance of CIC detection may be increased by the simultaneous demonstration of C4 and C3 A.P. and by making allowance for seasonal variations.

Relationship between Circulating Immune Complexes and Angiotensin‐Converting Enzyme in Pulmonary Sarcoidosis

The relationship between circulating immune complexes (CIC), serum angiotensin-converting enzyme (SACE) and clinical features was investigated in 119 patients with sarcoidosis. CIC, measured by the C1q-binding test and a polyethylene glycol precipitation test, were detected in 42% of the patients. A significantly higher level of CIC was found in patients with duration of the disease of more than 2 years and in patients in stage II or III on chest X-ray. SACE was increased in 45% of the patients, most frequently in those with active disease and in those in stage II or III on chest X-ray. No positive correlation was found between CIC and elevated levels of SACE.

40] Enzyme immunoassay for the demonstration and quantification of immune complexes

This chapter describes the enzyme immunoassay (EIA) for the demonstration and quantification of immune complexes (IC). The occurrence of circulating IC may be suspected in any patient, undergoing chronic antigenic stimulation. Variation of the level of rheumatoid factor (RF), hypocomplementemia, and presence of cryoglobulins are valuable indirect signs of the presence of IC in sera. The enzyme immunoassay is based upon the inhibition of the binding of a polyclonal RF (PRF) to an IgG-cellulose solid phase by IC in biological fluids. Its principle derives from that of the EIA for RF measurement, and comprises three steps that include: (1) elimination of endogenous RF present in some sera by adsorption onto an aggregated IgG-sepharose sorbent, (2) incubation of the adsorbed samples with a known amount of PRF, and (3) aggregated IgG cellulose. Results obtained with the IC-EIA were correlated with polyethylene glycol precipitation test and Clq binding activity. It is shown that the use of various binding agents leads to the detection of IC, differing by their size, antigen/antibody ratio, and classes of antibody.

Circulating immune complexes in patients with gram negative septic shock.

In order to explain complement components abnormalities observed during septic shock, circulating immune complexes (C.I.C.) were searched for in sera from 34 patients with gram negative sepsis by two different methods: polyethylene glycol precipitation test based on physical properties of C.I.C. and C1q deviation test based on the property of radiolabelled C1q to react with C.I.C. Serum immunoglobulins (IgG, IgA, IgM) and complement components (C1q, C3, C4) levels were simultaneously determined. Seventeen patients with minimal haemodynamic abnormalities had normal or increased levels (except C4 at 62% of normal) and in eleven cases both tests for C.I.C. were simultaneously positive. Seventeen patients with severe septic shock had a decrease in IgG, IgM C1q, C3 and C4 and none had both tests for C.I.C. simultaneously positive (P less than 10(-4)). The disappearence of C.I.C. in patients with severe septic shock associated with evidence of complement activation suggests their involvement in the pathogenesis of septic shock in man.