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Biomedical subjects

G C Zucchelli

Publications and source records attributed to G C Zucchelli.

At least 37 records · Page 2Linked to original sources
PubMed1992

Immunoassay of CEA, CA 19-9, CA 125, and CA 15-3 on the automated systems ES 300 and ES 600: methodological evaluation from a multicentre collaborative study.

The analytical performance of the automated Enzymun Test System ES 300 and ES 600 (developed by Boehringer Mannheim) for the assay of the tumour markers CEA, CA 19-9, CA 125, and CA 15-3, was assessed from data collected in a multicentre collaborative study in which eleven laboratories were involved. Results of the 1990 cycle of the external quality assessment (EQA) scheme for tumour markers, supported by the Italian National Research Council (CNR), were also used in this evaluation. The within-assay and between-assay precision was found to be 2.0 and 4.3 CV% for CEA, 2.9 and 6.8 CV% for CA 19-9, 3.6 and 9.4 CV% for CA 125, 2.9 and 6.0 CV% for CA 15-3. The between-lab variability of the four tumour markers on ES 300 and ES 600 systems was 9.4, 10.6, 11.9, 9.2 CV% for CEA, CA 19-9, CA 125 and CA 15-3 respectively. These values were comparable to or better than those obtained with the most precise manual kits used by laboratories participating in the 1990 EQA cycle. The agreement between the results from the Enzymun Test and those obtained using other method/kits was evaluated by assaying control samples previously circulated either in the CNR EQA or in the German EQA. The regression analysis indicates that for CEA, CA 125 and CA 15-3 assays the results produced by ES 300 and ES 600 are in good agreement with the consensus means of the EQAs; CA 19-9 results exhibit a worse correlation and are generally lower than the consensus mean. The linearity of the assays for the four tumour markers was checked by dilution tests performed by participants in the collaborative study; in all cases the dilution of the sample did not affect the values obtained.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1992

Interassay variability of immunometric methods for thyrotropin in an external quality assessment survey: evidence that functional sensitivity is not always adequate for clinical decisions.

We investigated the ability of current immunometric methods for thyrotropin (TSH; thyroid-stimulating hormone) to distinguish between low-normal and subnormal hormone concentrations by using the data from an external quality assessment (EQA) survey in 1990. We computed the interassay (between-run) precision profiles from results from 101 laboratories, which used the five most popular kits in the survey; during the control period (one year) each laboratory assayed 4 EQA pools distributed (as hidden replicates) in five occasions. The interassay CV was relatively low (9-13%) for three pools in the normal TSH range (greater than 0.8 milli-int. unit/L) but markedly higher (30-40%, except for one more precise kit) in the subnormal range (0.2 milli-int. unit/L). We calculated the effect of the between-run variability on the diagnostic accuracy (discrimination between normal and subnormal values) for three representative TSH concentrations: 0.2, 0.4, and 0.5 milli-int. unit/L (0.3 milli-int. unit/L was considered the lower normal limit). The three concentrations were reasonably discriminated (P less than or equal to 5%), and only one kit showed a between-run CV less than 18% at 0.2 milli-int. unit/L. For the other four less-precise kits, only the higher TSH value (0.5 milli-int. unit/L) could be classified with an acceptable diagnostic reliability. With the most precise kit, one can distinguish two TSH concentrations in the 0.3-0.5 milli-int. unit/L range that differ by at least 30%; with the other kits, differences greater than 50-60% are needed for reliable discrimination. Thus many laboratories fail to achieve the functional sensitivity of a second-generation assay, even if they use immunometric methods. TSH assays with a better interassay precision in the low concentration range are needed.

Humans↗
PubMed1991

The CNR external quality assessment program for immunoassays: statistical analysis and reports for participants.

The results collected in the CNR/Tecno-standard external quality assessment (EQA) program for immunoassays of hormones and tumor markers are computer-processed to prepare a "periodic" report and an "end-of-period" report to be sent back to the participants in the survey. The aim of the periodic report is to allow comparison between the result obtained by a laboratory on a single EQA sample with those of all the other laboratories and with the users of the same method/kit; the report contains a histogram of all results and the mean, SD, CV, median and range (computed after trimming of outliers). The same statistics are also reported for data grouped according to the method/kit used. The end of period report provide the participant with a scored estimate of individual analytical performance (average bias and average imprecision) achieved assaying all the EQA samples dispatched in the control cycle (usually a six-month period during which 12-18 samples have been assayed); this cumulative report contains estimates of the performance of those kits more widely used in the survey. Beside helping laboratories to monitor their performance against an external reference, the EQA allows the collection of a large amount of data from which the state of the art and trends in the quality of immunoassays can be soundly evaluated and documented. To achieve this aim, the average total variability is computed from all data collected in the EQA cycle; this index is used for comparing the between-laboratory agreement of different immunoassays and for demonstrating trends of the quality over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1991

External quality assessment of assays for hormones and tumor markers in Italian laboratories.

External quality assessment (EQA) programs run by CNR/Tecnostandard for immunoassays of hormones and tumor markers, started in 1980, presently include as many as 20 analytes; about 300 laboratories are involved in these programs. For all immunoassays submitted to the EQA, the inspection of cumulative results allows the current situation to be documented for total variability and its within-kit and between-kit components (the former accounting for the reproducibility and robustness of the kits and the latter for their systematic differences of estimation). For 13 assays subjected to EQA for longer, the variability trends over time are depicted, and single factors affecting the overall quality of particular assays are identified. Among these, experimental simplification of kit structure, alignment of calibrators with an acknowledged reference material, and adoption of monoclonal-antibody based two-sites assays can be mentioned. On the contrary, neither automation of the procedures nor (more expectedly) increasing use of nonisotopic techniques has proved effective in significantly improving the analytical quality.

Biomarkers, Tumor↗
PubMed1990

A new chemiluminescence immunoassay for triiodothyronine and thyroxine: evaluation using quality control sera assayed in an interlaboratory survey.

A recently developed chemiluminescence immunoassay system (LIA-mat) for triiodothyronine and thyroxine, set up by Byk-Sangtec Diagnostica (Dietzenbach, Germany), has been evaluated and compared with radioimmunoassays and with a chemiluminescence enhanced enzyme immunoassay (Amerlite), using control materials circulated in a national interlaboratory quality control, as well as patient sera. The LIA-mat assays are competitive methods which use coated monoclonal antibodies and triiodothyronine- or thyroxine-ABEI (aminobutylethylisoluminol) conjugate as tracers. The working range of LIA-mat T3 (computed from the within-assay precision profile) extended from 1.4 to 12.3 nmol/l; the between-assay precision was 8.1 - 19.3 CV%. Regression analysis of the LIA-mat T3 results (y) against the consensus means (x) of the participants in the national interlaboratory survey yielded: y = -0.14 + 1.05 x, r = 0.95. The working range of LIA-mat T4 extended from 33 to 515 nmol/l; the between-assay precision was 5.4 - 9.2 CV%. An excellent agreement was found between LIA-mat T4 results (y) and the consensus means (x) of the laboratories participating in the national interlaboratory survey (y = 3.79 + 1.02 x, r = 0.98).

Dose-Response Relationship, Drug↗
PubMed1990

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.

Adult↗
PubMed1989

A new luminescence immunoassay for thyrotropin using coated tubes: evaluation and comparison with immunoradiometric assay.

A recently available chemiluminescence immunoassay (LIA-MAT) for TSH, set up by Byk-Sangtec Diagnostica, has been evaluated and compared with IRMA methods. The system LIA-MAT uses two monoclonal antibodies: one coated on tubes and the other labelled with isoluminol. To compute the within-assay precision profile, we estimated the response error relationship from all the duplicates (420) of eleven experiments. The CV of the response was 4-5% from the maximal response until 10,000 RLU (corresponding to about 1 microIU/ml); in the lower response range the CV worsened up to 8%. The sensitivity, derived from the precision profile, was 0.052 microIU/ml similar to that found in IRMA-MAT (0.044 microIU/ml); the working range extended from 0.33 to 100 microIU/ml. Results from LIA-MAT in the concentration range 1-30 microIU/ml were compared with the consensus mean produced by users of IRMA methods (IRMA-MAT, IRMA-Behring, Maiaclone Serono) participating in an inter-laboratory survey; a good correlation with IRMA techniques was found. The distribution of TSH determinations produced by LIA-MAT on 62 low concentration sample (less than 0.3 microIU/ml) from patients unresponsive to TRH test, was found similar to that observed for the kit IRMA Boots-Celltech assumed as reference.

Evaluation Studies as Topic↗
PubMed1989

Methodological evaluation of a new chemiluminescence immunoassay for thyrotropin using acridinium ester-labelled antibody.

A recently available immunochemiluminometric assay (ICMA) for TSH developed by Ciba Corning Corp. has been evaluated. This system (Magic Lite) uses an acridinium-ester-labelled antibody and magnetizable particle for bound-free separation. In each assay only two calibrators are carried out and used to re-scale a manufacturer-generated curve stored in the memory of the luminometer. The precision of the response (RLU) estimated by all duplicates of 14 runs was about 4% for responses greater than 12,000 RLU (corresponding to a concentration interval 0.7-113 microIU/ml) and worsened in the lower range (up to 10% CV); the sensitivity, computed from the mean within-assay precision profile, was 0.028 microIU/ml; the between-assay precision ranged from 4.6 to 13.1 CV%. Regression analysis of ICMA results (y) against consensus values of Behring IRMA (x) on 15 QC sera assayed in an inter-laboratory survey (concentration range 1-30 microIU/ml) gave y = -0.003 + 0.98x indicating a good agreement of the two techniques. Similar conclusions have been derived from the comparison of the ICMA results (y) in the low TSH concentration range (less than 1 microIU/ml) against the IRMA Boots Celltech (x) on 80 patient samples (y = 0.04 + 1.04x).

Acridines↗
PubMed1989

The TDx assay for cyclosporine and its metabolites in blood samples compared with HPLC and RIA methods.

Two methodologies have been developed to monitor cyclosporine (CsA) therapy: high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA). Recently, a fluorescence polarization immunoassay (FPIA) has also become commercially available for the assay of CsA and its metabolites. The authors compared the results obtained with a modified FPIA with those found with two RIAs which use a polyclonal antibody, in order to verify if the FPIA assay is suitable for routine measurements in blood samples. Moreover, the accuracy of the RIAs and of the modified FPIA was checked against the results obtained by an HPLC technique assumed as a reference assay. The FPIA assay for CsA in blood samples seems preferable to the RIAs; in fact, as far as specificity is concerned, the TDx assay is comparable to polyclonal RIAs, while the precision (both within- and between-laboratories) is significantly better. Moreover, the TDx method is easier and faster to perform (20 samples can be assayed in about 30 min, while 2-4 h are necessary with RIA), with fewer handling steps; the instrumentation is automated and the reagents are more stable and less hazardous than those used in RIA.

Chromatography, High Pressure Liquid↗
PubMed1989

Serum interleukin-2 receptor levels measured by enzyme immunoassay in heart and kidney transplanted patients.

IL-2R serum concentrations were assayed by a sandwich enzyme immunoassay method in order to ascertain if the measurement of the soluble form of IL-2R can be considered a useful marker of allograft rejection in heart and kidney transplanted patients. Serum IL-2R levels increased significantly compared to pre-operated values (1129 +/- 215 U/ml vs. 592 +/- 209 U/ml, p less than 0.01) in six heart-transplanted patients during acute rejection crises documented by clinical findings and endomyocardial biopsy, and returned to baseline levels after successful treatment (544 +/- 395 U/ml vs. 1129 +/- 215 U/ml, p less than 0.01). Moreover, we observed that severe bacterial (n = 5) or viral (n = 2) infections were also accompanied by a significant increase of IL-2R serum levels in heart-transplanted patients (1076 +/- 263 U/ml vs. 486 +/- 146 U/ml, p less than 0.01 in bacterial, and 1290 +/- 368 U/ml vs. 370 +/- 85 U/ml in viral infections). In the six patients with renal transplant, the mean pre-operative IL-2R level was also elevated (1507 +/- 203 U/ml). A 1.5-4 fold increase of IL-2R levels has been observed at the beginning of both acute rejection and clinically evident infection. Our data show that the serum concentration of IL-2R is increased in heart and kidney transplanted patients during allograft rejection crisis. However, the information gained with this assay must be cautiously interpreted because an increase of IL-2R concentrations can also indicate bacterial or viral infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Evaluation and comparison of radioimmunoassay methods using monoclonal or polyclonal antibodies for the assay of cyclosporine in blood samples.

Results obtained measuring blood Cyclosporine A (CsA) concentrations in transplanted patients (124 samples of cardiac, 20 samples of liver, and 10 samples of kidney transplanted patients) by the use of two monoclonal radioimmunoassay (RIA) methods have been compared with those found using the HPLC technique (considered as the reference method) and two polyclonal RIAs. In addition, results on quality control samples collected in a multicentre collaborative study for CsA assay from the users of the same monoclonal and polyclonal RIAs were analysed to evaluate the performance of the methods under study. Polyclonal RIAs, which measure both the parent molecule and its metabolites, produced results 1.5-3 times higher than HPLC or monoclonal RIAs. On the contrary the two RIAs, which use monoclonal antibodies specific for CsA, show a better correlation with HPLC; these RIAs, which measure the intact drug molecule only, are recommended when the monitoring of the native molecule of CsA is requested. As far as the reproducibility is concerned, the four RIAs (both polyclonal and monoclonal) exhibit an unsatisfactory degree of between-assay and between-lab precision, since the coefficients of variation (CVs) ranged from 19.4% to 23.1%.

Antibodies↗
PubMed1987

Plasma met-enkephalin and leu-enkephalin in chronic renal failure.

Plasma met-enkephalin and leu-enkephalin has been measured in a group of 28 patients with chronic renal failure, to discover whether these opioids are affected by standard haemodialysis and haemofiltration. Met-enkephalin was markedly higher (P less than 0.001) in uraemic patients than in a group of 13 normal subjects, and was directly related to plasma creatinine (r = 0.60; P less than 0.01) and to plasma urea (r = 0.36; P = 0.06). In contrast, leu-enkephalin was suppressed in uraemic patients (P less than 0.001). Met-enkephalin fell slightly but significantly (P less than 0.02) after both haemodialysis and haemofiltration; however, on average it remained at concentrations four times higher than normal. No changes in plasma leu-enkephalin were observed after haemodialysis and haemofiltration. The cause(s) of the altered plasma concentrations of these opioid substances remains to be clarified.

Adult↗
PubMed1986

Minimizing between-kit variability in immunoassay for carcinoembryonic antigen by use of a common standard.

Between-laboratory agreement of CEA determinations collected in a multicenter study has been substantially improved (CV decreased from 60.4 to 21.6%) by converting the results from mass concentration units (ng/mL) of local kit standards to int. units/L of the international standard first IRP 73/601. Conversion factors for the kits most used were computed, during the same survey, from results of two analytical-recovery experiments in which control samples, supplemented with the international standard, were analyzed by participating laboratories (n = 96).

Carcinoembryonic Antigen↗
PubMed1986

Components of variance analysis of data produced in a national quality-control survey of radioimmunoassays of thyroxin, triiodothyronine, thyrotropin, prolactin, and progesterone.

Data collected in a collaborative survey for radioimmunoassays have been studied by using analysis of variance to estimate the within-kit (CVw.kit) and the between-kit (CVb.kit) components of the total variability (CVT). This analysis has been applied to the results for triiodothyronine, thyroxin, thyrotropin, prolactin, and progesterone produced by 80-150 laboratories that assayed blind, replicate samples. Total variability was lowest in the thyroxin assay (CVT = 10.9%), associated with a very close between-kit agreement (CVb.kit = 4.0%); in the triiodothyronine assay, on the other hand, the large between-kit component (CVb.kit = 10.1%) increased the total variability to 16.1%. In the prolactin assay the CVT of 19.3% included 17.5% CVw.kit and 8.1% CVb.kit. Assays for thyrotropin and progesterone involve analyses of two pools at different hormone concentrations. The CVb.kit component was very high in the low-concentration pool, both for thyrotropin (25.1%) and progesterone (45.2%); in the higher-concentration pool it decreased to 8.3% for thyrotropin but remained high (21.6%) for progesterone. Applying analysis of variance to the triiodothyronine and thyroxin data obtained by different laboratories using the same kit showed that most kits yielded significantly different measurements when used in different laboratories.

Analysis of Variance↗
PubMed1984

Progress report on a national quality-control survey of triiodothyronine and thyroxin assay.

In January 1980, a national external quality-control survey was organized to evaluate assays for triiodothyronine (T3) and thyroxin (T4). Currently, about 150 laboratories are involved. Each participant has received and assayed 100 quality-control samples during four periods of about six months each. The average analytical performance achieved by the participants in each six-month period was estimated by computing the average between-laboratory agreement (CVT), the overall average bias, and the average laboratory imprecision. During the 2.5 years of the survey, analytical performance has improved for both assays (CVT decreased from 17.0 to 15.7% for T3 and from 13.1 to 12.7% for T4). Analysis of survey results according to the method/kit used (mean kit bias and kit imprecision for the nine kits most used by participants) showed that the analytical reliability of the T4 assay is generally better than that observed for T3, mainly because of the larger systematic differences among T3 kits.

Chemistry, Clinical↗