Interference by heterophilic antibodies in immunoassays: wrong increase of myoglobin values

Aim of this work is to illustrate how analytical interference in immunoassay may produce serious errors in clinical laboratory results. The sophisticated quality assurance schemes used in many laboratories do not identify erroneous results arising from aberrant samples. Recently attention has been focused on the incidence and implication of false-positive results arising from the presence of certain substances in a patient's serum that interfere with one or more steps in immunoassays. In this paper, we present the case of a 92 year-old woman whose plasma myoglobin concentrations falsely increased when measured using the Beckman Access assay. We demonstrated that heterophilic antibodies accounted for the falsely increased myoglobin values, and we suggest how to resolve such situations.

Anti-68 kDa antibodies in autoimmune sensorineural hearing loss: are these autoantibodies really a diagnostic tool?

OBJECTIVES

Autoimmune sensorineural hearing loss (ASNHL) is a relatively rare disorder which can lead to total deafness. At present, no specific laboratory test with adequate sensitivity and specificity is available to confirm the clinical suspicion of ASNHL. The aim of this study was to identify if evaluation of anti-hsp70 antibodies is an accurate diagnostic tool in patients affected by ASNHL.

STUDY DESIGN

Prospective study.

METHODS

During 4-year (2001-2005), all patients with SNHL who were referred to the Eye, Ear, Nose and Throat Department of Parma University, Italy, underwent specific tests to determine the autoimmune origin of the disease. Patients with a consistent suspicion of ASNHL underwent the routine serologic tests and a test for determination of anti-hsp70 antibodies. The same patients were divided into three groups: (1) idiopathic ASNHL; (2) ASNHL associated with ocular inflammation, i.e. Cogan's Syndrome; (3) ASNHL associated with a systemic autoimmune disease (SAD). The control group included: (1) healthy subjects; and (2) patients affected by SAD, without any ocular or audiovestibular disease.

RESULTS

88 subjects (67 patients, defined as "study group", and 21 controls) were evaluated. Anti-hsp70 antibodies were isolated in 52% of the study group patients, and in 4% of the control group (chi2 = 13.009, p < 0.01). In the idiopathic ASNHL patients, 59.5% were found positive for anti-hsp70 antibodies. About 50% of patients affected by CS and 37.5% of patients affected by SAD with SNHL were found positive. In the control group, anti-hsp70 antibodies were found in 8.3% of healthy subjects and in none of the patients with SAD and no hearing loss.

CONCLUSIONS

The present study confirms the value of the anti-hsp70 test in the serological diagnosis of autoimmune hearing loss. It is still the only available diagnostic marker that identifies an autoimmune origin of hearing loss.

Are thyroid function tests too frequently and inappropriately requested?

In spite of data supporting the use of the serum thyrotropin (TSH) concentration as the best test to detect abnormal thyroid function, measurement of circulating thyroid hormones with or without a serum TSH continues to be frequently requested to evaluate thyroid function. We have analyzed how combinations of thyroid function tests were ordered by referring physicians and the results of the tests in order to offer some suggestions as to how to use thyroid function tests in a cost effective manner. During 1995, 19,181 inpatient and outpatient requests (45,865 different tests) for thyroid function tests were received by the laboratory of a 1600 bed University Hospital in Parma, Italy. The following tests were carried out: T4, free T4, T3, free T3 and TSH. Serum TSH values below and above the normal range were considered to reflect abnormal thyroid function i.e. hyperthyroidism, or hypothyroidism including subclinical disease independent of the results of the other tests. Combinations of ordered tests and the percent of the total for each combination were: TSH+T4+T3 (56%), TSH+FT4+FT3 (14%), TSH (12%), TSH+FT4 (9%), TSH+T4 (1%), TSH+T4+T3+FT4+FT3 (5%), others (3%). The T4+T3+TSH panel (10,780 requests) had normal serum TSH values in 80.6% and the FT4+ FT3+TSH panel (2,590 requests) had normal TSH values in 73.2%. Elevated serum TSH concentrations were observed more frequently in hospitalized than in ambulatory patients (9.7% vs 7.4% p<0.001). T3 (elevated serum T3, normal T4 and low TSH concentrations) and T4 (elevated serum T4, normal T3 and low TSH concentrations) toxicosis were observed in 8.1% and 9.4%, respectively, of the requested test (NS). FT3 and FT4 toxicosis, defined as for T3 and T4 toxicosis, were observed in 7.5% and 4.9%, respectively (NS). The low T3 and low FT3 syndrome in hospitalized patients was present in 1.6% and 2.3% of the requests, respectively (NS). The low T4+low T3 and low FT4+low FT3 syndrome was present in only 0.3% and 0.2%, respectively, of the requests. Our study shows that a) in hospitalized patients thyroid function tests were requested in 20% of the patients and only one in 14 of these patients at the highest could have abnormal thyroid function, as indicated by abnormal TSH value b) FT4 (or T4) is as useful as FT3 (or T3) in the diagnosis of hyperthyroidism, c) in hospitalized patients the low T3 syndrome was far less common than that reported in the literature, probably due to the lower severity of illness, d) panels which include T3 and FT3 are not justified, and e) serum TSH alone is the most appropriate initial thyroid function test.

Serotonergic function after (+/-)3,4-methylene-dioxymethamphetamine ('Ecstasy') in humans

(+/-)3,4-Methylene-dioxymethamphetamine (MDMA, or 'Ecstasy') effects on serotonin system function and behaviour in humans are unclear. Fifteen MDMA users, who did not have other drug dependencies or alcohol abuse, and had not used other drugs for prolonged periods, and 15 control individuals were included in a study to assess the biological and psychological changes after chronic use of MDMA. Prolactin and cortisol responses to D-fenfluramine challenge, clinical psychobehavioural changes, personality characteristics, including mood, aggressiveness and temperamental aspects, were evaluated 3 weeks after MDMA discontinuation. MDMA users had significantly reduced prolactin and cortisol responses in comparison with control individuals (p < 0.001 and p < 0.005, respectively). Dysphoria and mood changes were exhibited in seven individuals, tiredness in five and sensation-seeking behaviour in twelve at the clinical evaluation. Significantly higher scores were found in MDMA individuals than in control individuals for Minnesota Multiphasic Personality Inventory subscale for Depression, for Buss Durkee Hostility Inventory direct and guilt subscales, for Hamilton Depression Rating Scale and for novelty-seeking Tridimensional Personality Questionnaire subscale. Prolactin responses to D-fenfluramine stimulation area under the curve among MDMA users were negatively correlated with direct aggressiveness scores for Buss Durkee Hostility Inventory; a negative correlation between prolactin responses and novelty-seeking scores was also evidenced among MDMA users. These data suggest an association between serotonin system impairment and MDMA use in humans; in interpretation of these results, the possibility that serotonin deficit in MDMA individuals was partially related to a premorbid condition, in relationship with novelty-seeking behaviour and mood disorders, can not be excluded.

Serotonergic function in mothers of opioid addicts: correlation with comorbid depression

The serotonergic (5-HT) function of 36 mothers of heroin addicts, of whom 16 subjects were without psychopathological features (group A) and 20 subjects had major depressive disorders (group B), as well as 10 age- and sex-matched healthy controls, was examined by L-D-fenfluramine stimulation of secretion of prolactin (PRL) and cortisol. The subjects' addict relatives were also tested for personality features and hormonal responses to L-D-fenfluramine. The PRL and cortisol responses to the stimulus were normal in mothers of group A, and blunted in mothers of group B. A high frequency (70%) of heroin addicts with comorbid depression was found among the sons of group B mothers. The sons of depressed mothers showed reduced PRL and cortisol responses to fenfluramine. A significant direct correlation has been demonstrated between the PRL areas under curves (AUC) of mothers and sons in response to the 5-HT agonist. Our data suggest that genetic 5-HT impairment is not involved in the pathogenesis of heroin addiction or codependence per se, and is probably linked to the presence of familial depression in comorbidity with the addictive disorder.

Neurotransmitter-neuroendocrine responses to experimentally induced aggression in humans: influence of personality variable

Aggressiveness was experimentally induced in 30 psychophysically healthy male subjects, 18-19 years old, divided into 15 cases with low normal and 15 with high normal basal aggressivity. Plasma norepinephrine (NE), epinephrine (EPI), growth hormone (GH), prolactin (PRL), cortisol (CORT) and testosterone (Te) concentrations were measured in basal conditions and during experimentally induced aggressiveness. Basal Te and stimulated NE, GH and Cort levels were higher in subjects with high-normal than in those with low-normal aggressiveness, suggesting that the functional tonus of the NE system and of the NE-dependent hormonal axes might be a modulator of the behavioral parameter.

Serum cardiac troponin T after repeated endurance exercise events

Recently Dr. Rowe made a hypothesis according to which small areas of myocardial necrosis can be caused by microvascular spasm, related to high catecholamine concentrations and other mechanisms, following extraordinary unremitting endurance exercises or due to the cumulative effect of several endurance events. It was this last suggestion which prompted us to investigate 25 top cyclists, taking part in the 77th Giro d'Italia. Blood samples were obtained the day before the start of the competition and once a week thereafter until the end. We measured myoglobin, lactic dehydrogenase, total creatine kinase, creatine kinase isoenzyme MB and serum cardiac troponin T (Tn-T), a highly sensitive and specific method for the detection of myocardial injury. While at measuring time points which followed we found a significant increase in the serum indicators of muscle damage, compared with their values at the beginning of the race, creatine kinase isoenzyme MB did not rise significantly and cardiac Tn-T was found in the serum of only 5 athletes, repeatedly in some cases, but always below the cut off values considered as indicating myocardial ischemia. On the basis of the behaviour of creatine kinase isoenzyme MB and, above all, of cardiac Tn-T, we can conclude that heavy endurance exercises, repeated daily for 22 days, as was the case in our study, do not seem able to produce, in top athletes, permanent heart damage by means of acute myocardial injury.

Neuroendocrine responses to emotional arousal in normal women

The neuroendocrine effects of many stressful challenges and experimentally induced emotional states have been investigated in humans, but few data are available concerning the psychobiological correlates of the emotional arousal induced by TV violence, fear and conflictual emotions. In this study we evaluated cardiovascular, hormonal and mood changes induced by the view of a violent or, in random order, neutral movie in 20 healthy young women. The emotional arousal was associated with a significant increase in heart rate, systolic blood pressure and significant changes in self-evaluated mood states. beta-Endorphin, adrenocorticotrophic hormone, epinephrine and growth hormone showed a significant increase during emotional arousal, with a significant interaction mood-time. Cortisol increased significantly during the violent movie (areas under curves analysis), but not significant interaction mood-time has been demonstrated. Prolactin and norepinephrine levels did not show a significant change during the emotional stimulus. Our data evidence the existence of neuroendocrine changes associated with the defence mechanism and aroused by movie violence and conflictual situations.

Alpha-1- and 2-adrenoceptor subsensitivity in siblings of opioid addicts with personality disorders and depression

Noradrenergic receptor sensitivity of 16 healthy male siblings of heroin addicts and of 8 age and sex-matched controls was examined by administering a clonidine stimulation test and by measuring the resulting growth hormone (GH) (alpha-2-adrenoceptors) and beta-endorphin (beta-endorphin) (alpha-1-adrenoceptors) responses. Siblings were divided into two groups: A = siblings of heroin addicts with personality disorders and high aggressivity and B = siblings of heroin addicts without mental disorders. The GH and beta-endorphin responses to clonidine were blunted in group A subjects compared with controls and normal in group B.

Parental divorce and neuroendocrine changes in adolescents

Plasma noradrenaline (NE), adrenocorticotrophic hormone (ACTH), growth hormone (GH), prolactin (PRL) and luteinizing hormone (LH) concentrations were examined in basal conditions and after stimulation by the step test in two groups of psychophysically healthy adolescent girls, 18 from divorced families and 16 from non-divorced families. Basal NE, ACTH, GH, PRL values did not differ in the two groups, whereas those of LH were significantly lower in the adolescents from divorced parents than in those from non-divorced families. Responses of NE and ACTH to the stimulus were normal, of GH and PRL were weaker, and of LH slightly weaker in children of divorced parents. An impaired catecholaminergic and serotoninergic tonus in children of disrupted families might underly the hormonal alterations.

Cholesterol crystals in biliary microlithiasis

A recent study put forward the hypothesis that microlithiasis may represent an early stage in the development of biliary calculi. It is an established fact that cholesterol crystals are the product of an inevitable stage in the sequence leading to gallstone formation. To test the hypothesis stated above ten patients affected by gallbladder cholesterol microlithiasis (CM) were examined in the lipid composition of the bile, the cholesterol saturation index and the presence of cholesterol crystals being calculated. The results were compared with those of 14 patients affected by pigment microliths, 24 with larger stones (LS) and ten control patients. The cholesterol saturation index was above one in all CM patients, whereas in some LS patients the gall-bladder bile was not supersaturated. Cholesterol crystals were observed in the gallbladders of all CM patients and seven LS patients. These results would seem to provide support for the hypothesis of microcalculi as being "young stones", with the bile of CM patients maintaining the conditions leading to gallstone formation.

Possible effect of caerulein on calcitonin secretion in man

Caerulein, infused in normal subjects, significantly reduces serum Calcium levels; in addition, when infused 60 or 90 min after radioactive calcium, it increases the specific plasma radioactivity, in a manner similar to calcitonin. These results suggest that in man caerulein stimulates calcitonin release.