Influence of therapeutic plasma exchange treatment on short-term mortality of critically ill adult patients with sepsis-induced organ dysfunction: a systematic review and meta-analysis

INTRODUCTION

The impact of therapeutic plasma exchange (TPE) on short-term mortality in adult patients with sepsis-induced organ dysfunction remains uncertain. The objective of the study is to assess the effect of adjunct TPE in this setting through a comprehensive literature review.

METHODS

The National Library of Medicine's Medline, Ovid (Embase), the Cochrane Library database and clinicaltrial.gov from January 01, 1966, until October 01, 2022, were searched for terms: therapeutic plasma exchange, plasmapheresis, sepsis, and septic shock. We reviewed, selected and extracted data from relevant randomized clinical trials (RCTs) and matched cohort studies (MCSs) comparing short-term mortality in critically ill adult septic patients treated with standard therapy versus those receiving adjunct TPE. Risk of bias was assessed in the RCTs using Cochrane Collaboration tool and in MCSs using ROBINS-I tool. Summary statistics, risk ratios (RRs), and confidence intervals (CIs) were calculated using random effects model.

RESULTS

This systematic review included 937 adult critically ill septic patients from five RCTs (n = 367) and fifteen MCSs (n = 570). Of these total, 543 received treatment with TPE in addition to standard care. The meta-analysis includes all five RCTs and only six MCSs (n = 627). The adjunct TPE treatment (n = 300) showed a significant reduction in short-term mortality (RR 0.59, 95% CI 0.47-0.74, I2 3%) compared to standard therapy alone (n = 327). The systematic review of all 20 trials revealed that adding TPE to the standard therapy of critically ill septic patients resulted in faster clinical and/or laboratory recovery.

CONCLUSIONS

Our comprehensive and up-to-date review demonstrates that adjunct TPE may provide potential survival benefits when compared to standard care for critically ill adult patients with sepsis-induced organ dysfunction. While results of this meta-analysis are encouraging, large well-designed randomized trials are required to identify the optimal patient population and TPE procedure characteristics prior to widespread adoption into practice.

Baseline Serum Prostate-specific Antigen Value Predicts the Risk of Subsequent Prostate Cancer Death-Results from the Norwegian Prostate Cancer Consortium

BACKGROUND

Prostate-specific antigen (PSA) levels in midlife are strongly associated with the long-term risk of lethal prostate cancer in cohorts not subject to screening. This is the first study evaluating the association between PSA levels drawn as part of routine medical care in the Norwegian population and prostate cancer incidence and mortality.

OBJECTIVE

To determine the association between midlife PSA levels <4.0 ng/ml, drawn as part of routine medical care, and long-term risk of prostate cancer death.

DESIGN, SETTING, AND PARTICIPANTS

The Norwegian Prostate Cancer Consortium collected >8 million PSA results from >1 million Norwegian males ≥40 yr of age. We studied 176 099 men (predefined age strata: 40-54 and 55-69 yr) without a prior prostate cancer diagnosis who had a nonelevated baseline PSA level (<4.0 ng/ml) between January 1, 1995 and December 31, 2005.

INTERVENTION

Baseline PSA.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We assessed the 16-yr risk of prostate cancer mortality. We calculated the discrimination (C-index) between predefined PSA strata (<0.5, 0.5-0.9, 1.0-1.9, 2.0-2.9, and 3.0-3.9 ng/ml) and subsequent prostate cancer death. Survival curves were plotted using the Kaplan-Meier method.

RESULTS AND LIMITATIONS

The median follow-up time of men who did not get prostate cancer was 17.9 yr. Overall, 84% of men had a baseline PSA level of <2.0 ng/ml and 1346 men died from prostate cancer, with 712 deaths (53%) occurring in the 16% of men with the highest baseline PSA of 2.0-3.9 ng/ml. Baseline PSA levels were associated with prostate cancer mortality (C-index 0.72 for both age groups, 40-54 and 55-69 yr). The fact that the reason for any given PSA measurement remains unknown represents a limitation.

CONCLUSIONS

We replicated prior studies that baseline PSA at age 40-69 yr can be used to stratify a man's risk of dying from prostate cancer within the next 15-20 yr.

PATIENT SUMMARY

A prostate-specific antigen level obtained as part of routine medical care is strongly associated with a man's risk of dying from prostate cancer in the next two decades.

Rapid diagnosis and reduced workload for urinary tract infection using flowcytometry combined with direct antibiotic susceptibility testing

BACKGROUND

We evaluated if flowcytometry, using Sysmex UF-5000, could improve diagnosis of urinary tract infections by rapid identification of culture negative and contaminated samples prior to culture plating, thus reducing culture plating workload and response time. We also evaluated if it is possible to reduce the response time for antibiotic susceptibility profiles using the bacteria information flag on Sysmex UF-5000 to differentiate between Gram positive and negative bacteria, followed by direct Antibiotic Susceptibility Testing (dAST) on the positive urine samples.

METHODS

One thousand urine samples were analyzed for bacteria, white blood cells and squamous cells by flowcytometry before culture plating. Results from flowcytometric analysis at different cut-off values were compared to results of culture plating. We evaluated dAST on 100 urine samples that were analyzed as positive by flowcytometry, containing either Gram positive or Gram negative bacteria.

RESULTS

Using a cut-off value with bacterial count ≥100.000/mL and WBCs ≥10/μL, flowcytometry predicted 42,1% of samples with non-significant growth. We found that most contaminated samples contain few squamous cells. For 52/56 positive samples containing Gram negative bacteria dAST was identical to routine testing. Overall, there was concordance in 555/560 tested antibiotic combinations.

CONCLUSION

Flowcytometry offers advantages for diagnosis of urinary tract infections. Screening for negative urine samples on the day of arrival reduces culture plating and workload, and results in shorter response time for the negative samples. The bacteria information flag predicts positive samples containing Gram negative bacteria for dAST with high accuracy, thus Antibiotic Susceptibility Profile can be reported the day after arrival. For the positive samples containing Gram negative bacteria the concordance was very good between dAST and Antibiotic Susceptibility Testing in routine. For positive samples containing Gram positive bacteria the results were not convincing. We did not find any correlation between epithelial cells and contamination.

Abstract 481: Utility of hCG as a biomarker of treatment response in advanced urothelial cancer: A population based series at Akershus University Hospital, Norway

Background

Treatment options in patients with advanced urothelial carcinoma (aUC) have improved significantly in the last decade, highlighting the need for adequate biomarkers. High tumor CGB5 mRNA, encoding Human Chorionic Gonadotrophin β (hCGβ) and elevated serum free hCGβ are related to poorly differentiated UC and correlated to poor prognosis. Hypothetically, hCG could be used as serum tumor marker in aUC patients.

Patients and methods

From December 2018 to November 2020, serum hCG levels were measured in 62 aUC patients referred to the oncology department, Akershus University Hospital. Median age 68 years, 42 male and 21 female. Total serum hCG (intact hCG + free hCGβ) was measured by electrochemiluminescence immunoassay “ECLIA”. In order to compensate for hypogonadism-related increases, hCG ≥ 50% above upper normal limit was considered as being elevated (hCG+), otherwise it was considered negative (hCG-). Further, hCG levels were defined as increasing (↑) or declining (↓) at treatment evaluation and follow up. Radiologically, patients had newly diagnosed disease (ND), progressive disease (PD) or non-PD (stable disease, partial or complete response) according to RECIST 1.1 at evaluation and follow up. hCG values were correlated with radiological findings at diagnosis, during and after treatment. Statistics by 2 x 2 contingency table and Chi Square (χ2) test.

Results

At least one hCG+ value was measured in 38 of 62 patients (61%), range 0.8 - 62,700 IU/L, and hCG was elevated in 22 of 43 patients (51%) with available hCG value at diagnosis, mean 15 IU/L (range 0.8 - 58). In total 213 hCG measurements could be correlated with concomitant CT or MR scans. At radiologic evaluation of ND & PD, hCG+/↑ and hCG -/↓ was found in 62 and 50 measurements, respectively. At non-PD, hCG -/↓ and hCG+/↑ was found in 94 and 7 measurements, respectively. For ND & PD versus non-PD, hCG showed a sensitivity and specificity of 55% and 93% respectively (95% CI 46-65% and 86-97%), positive and negative predictive value of 90% and 65% (95% CI 81-95% and 60-70%) and accuracy of 73% (95% CI 66-79%), χ2: p&lt;0.00001. Exclusion of the 24 patients without elevated hCG showed improved sensitivity 76% at the cost of lower specificity 82% (95% CI 65-85% and 66-92% respectively), positive and negative predictive value 90% and 63% (95% CI 82-95% and 52-72%) and accuracy of 78% (95% CI 70-86%), χ2: p&lt;0.00001.

Conclusions

Ectopic hCG production was observed in 61% of aUC patients with a strong and meaningful correlation between hCG changes and radiologic evaluation of treatment response. Intriguingly, hCG increase sometimes preceded radiologic PD, thus categorized as “false positive” until subsequent radiologic PD. hCG appears to be a promising tumor marker for biochemical treatment response evaluation in aUC patients.

Citation Format: Katarina Puco, Johan Bjerner, Stig Müller, Gunder M. Lilleaasen, Haldor Husby, Mattias Røed-Undlien, Daniel Heinrich, Fredrik A. Dahl, Oluf D. Røe, Jan Oldenburg. Utility of hCG as a biomarker of treatment response in advanced urothelial cancer: A population based series at Akershus University Hospital, Norway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 481.

Interference of common haemoglobin variants with the Tosoh G7 standard mode HbA1c method

BACKGROUND

HbA1c methods may be prone to interference by the presence of haemoglobin variants. In contrast to the variant mode of the HbA1c method on the Tosoh G7 instrument, the literature lacks investigations of haemoglobin variant interference with the standard mode. The current study sought to investigate whether different haemoglobin variants interfere with the Tosoh G7 standard mode HbA1c method, and whether present haemoglobin variants are identifiable on respective chromatograms.

METHODS

Samples routinely analyzed for HbA1c and suspected of having haemoglobin variants (N = 103) were included. HbA1c was measured on a Tosoh G7 in standard mode (Tosoh Corporation, Japan), and on the DCA Vantage (Siemens, Germany). Haemoglobin variants were identified using the VARIANT(™)β-Thalassemia Short Program (Bio-Rad Laboratories, Hercules, CA, USA) and by DNA sequencing.

RESULTS

The Tosoh G7 in standard mode measured significantly lower HbA1c results (between 1.0 and 2.5 percentage points absolute bias corresponding to between 11 and 27 mmol/mol, p < 0.001) in samples in which common haemoglobin variants (HbS, HbC, HbD or HbE) were present (n = 61). No significant difference in HbA1c (0.04 percentage points, p = 0.74) was found between Tosoh G7 standard mode and DCA Vantage in samples in which haemoglobin variants were absent (n = 36). In contrast to HbS and HbD, HbE and HbC trait could be identified on respective chromatograms.

CONCLUSION

The presence of common haemoglobin variants results in falsely low HbA1c measurements on the Tosoh G7 in standard mode. HbS and HbD trait are not identifiable on respective haemoglobin chromatograms.

Longitudinal Serum Testosterone, Luteinizing Hormone, and Follicle-Stimulating Hormone Levels in a Population-Based Sample of Long-Term Testicular Cancer Survivors

Purpose

To assess longitudinal long-term alterations of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in testicular cancer survivors (TCSs).

Patients and Methods

In all, 307 TCSs treated from 1980 to 1994 provided blood samples after orchiectomy but before further treatment, at Survey I (SI; 1998-2002), and Survey II (SII; 2007-2008). Levels of sex hormones were categorized according to quartiles and reference range (2.5 and 97.5 percentiles) of 599 controls for each decadal age group. TCSs were categorized according to treatment: surgery, radiotherapy (RT), or chemotherapy (CT). The risk of higher (LH) or lower (testosterone) levels was assessed with χ2 test (FSH) or ordinal logistic regression analysis and expressed as odds ratios (ORs) with 95% CIs.

Results

Risk of lower testosterone and higher LH and FSH levels was significantly increased for TCSs at all time points after RT or CT. At SII, ORs were 3.3 (95% CI, 2.3 to 4.7) for lower testosterone categories and 5.2 (95% CI, 3.5 to 7.9) for RT and CT. ORs for increased LH and FSH were 4.4 (95% CI, 3.1 to 6.5) and 18.9 (95% CI, 11.0 to 32.6) for RT, respectively, and 3.6 (95% CI, 2.4 to 5.3) and 14.2 (95% CI, 8.3 to 24.4) for CT, respectively. The cumulative platinum dose was significantly associated with risk of higher LH levels at both surveys and higher FSH at SI. In total, half the TCSs had at least one of three sex hormone levels outside the reference range at SII.

Conclusion

Long-term TCSs are at risk of premature hormonal aging. Our findings may pertain to cancer survivors in general, underlining the importance of extended follow-up.

Anatomic distribution of Neisseria gonorrhoeae, Chlamydia trachomatis and Mycoplasma genitalium infections in men who have sex with men

Background New cases of gonorrhoea (Neisseria gonorrhoeae) and chlamydia (Chlamydia trachomatis) infections have been steadily increasing in Scandinavian countries over the last decade. There is a particular urgency in reducing new infections as isolation of multiple drug resistant strains of gonorrhoea is becoming more frequent. The aim of this study was to determine the prevalence and sites of infection of common sexually transmissible infections (STIs) in men who have sex with men (MSM). Methods: We have performed a retrospective analysis of the three major STIs, gonorrhoea, chlamydia and Mycoplasma genitalium in urogenital, anorectal and oropharyngeal samples from MSM that attended two STI clinics in Oslo. Results: One hundred and thirty-six men (6.0%) out of 2289 MSM tested were found to be positive for gonorrhoea using a porA gene targeted nucleic acid amplification test (NAAT). Of these, 106 (77.9%) would not have been identified through testing first-void urine alone. Two hundred and twenty eight (10.0%) patients from 2289 tested were found to be positive for chlamydia, 164 (71.9%) of which were identified through anorectal specimens. Ninety-one (5.1%) patients from 1778 tested were found to be positive for M. genitalium, with 65 (71.4%) identified through testing of anorectal specimens. Conclusions: Our results supports the European findings that the MSM population carries a high burden of STIs and that testing the anorectum and oropharynx will identify a significantly higher percentage of infected patients and reservoirs of STIs.

Belief is only half the truth--or why screening for heterophilic antibody interference in certain assays makes double sense

BACKGROUND

Interference in immunoassays may cause both false-negative and false-positive results. It may be detected using a number of affirmative tests such as reanalysis of certain samples using different assay platforms with known bias, after the addition of blocker antibodies, or assessment of linearity and parallelism following serial doubling dilutions. One should look for interference where it is likely and has high medical impact. Probabilistic Bayesian reasoning is a statistical tool to identify samples where interference is most likely. But when looking for interference where it is likely, do we find it where it has the largest population health consequences?

METHODS

We used information theory to quantify the effect of assay interference by calculating the Shannon information content (using logarithms with base 2). We then obtained lower bounds of the population health consequences of a particular test and combined these expressions to get lower bounds of the population health consequences of interference.

RESULTS AND CONCLUSION

We suggest that assays having a low frequency of true positives should be the primary target of retesting because: (i) assays with a low frequency of true positives exhibit a high likelihood of interference and (ii) the population health consequences of false-positive results are generally higher for assays with a low frequency of true positives. Finally, we give a worked example having a realistic frequency of interference and test costs. In some immunoassays (e.g., tumour markers), adding a blocker to all tests can be a more cost-efficient mean than retesting positive samples.

The mild inflammatory response in febrile neutropenic lymphoma patients with low risk of complications is more pronounced in patients receiving tobramycin once daily compared with three times daily

We evaluated inflammatory markers in febrile neutropenic lymphoma patients undergoing high-dose chemotherapy with autologous stem cell support. Based on MASCC scores, our patients had a low risk of serious complications and a perspective of a benign initial clinical course of the febrile neutropenia. We also studied the impact of tobramycin given once versus three times daily on these immune markers. Sixty-one patients participating in a Norwegian multicentre prospective randomized clinical trial, comparing tobramycin once daily versus three times daily, given with penicillin G to febrile neutropenic patients, constituted a clinically homogenous group. Four patients had bacteraemia, all isolates being Gram-positive. Thirty-two patients received tobramycin once daily, and 29 patients received tobramycin three times daily. Blood samples were taken at the onset of febrile neutropenia and 1-2 days later. All samples were frozen at -70 °C and analysed at the end of the clinical trial for C-reactive protein (CRP), procalcitonin (PCT), complement activation products, mannose-binding lectin (MBL) and 17 cytokines. We found a mild proinflammatory response in this series of patients. CRP was non-specifically elevated. Ten patients with decreased MBL levels showed the same mild clinical and proinflammatory response. Patients receiving tobramycin once daily showed a more pronounced proinflammatory response compared with patients receiving tobramycin three times daily. Overall, febrile neutropenic cancer patients with a benign clinical course show a mild proinflammatory immune response.

Heterophilic antibody interference in commercial immunoassays; a screening study using paired native and pre-blocked sera

Heterophilic antibodies are still an important source of interference in immunoassays. We have conducted a screening study for interference in a panel of commercially available assays using two sera known to contain high titer Fc-reactive heterophilic antibodies.

The sera were distributed to laboratories participating in the Nordic External Quality Assessment cooperation (EQANord). Duplicate samples pre-blocked with aggregated murine monoclonal MAK33 were also supplied. Discrepancies (>50%) between the results for native and blocked samples were used to classify the tested assays as susceptible to interference. A total of 170 different assay kits covering 91 analytes were tested.

We found that 21 assays, covering 19 different analytes, were susceptible to interference from the heterophilic antibodies in the two sera. Many of these are clinically and commercially important assays. Some of the false results were grossly elevated and could have been detrimental to patient care in a clinical setting.

Heterophilic antibodies with Fc-reactivity remain a threat. A more widespread use of antibody fragments and aggregated immunoglobulin could potentially improve the heterophilic antibody resistance of assays intended for clinical use.

[The Swedish Chlamydia mutant nvC trachomatis in Norway]

BACKGROUND

A mutant Chlamydia trachomatis variant (nvC trachomatis) has made it more difficult to diagnose chlamydia in Sweden. The proportion of nvC trachomatis has varied between Swedish counties (25-80 %) in the period 2006-07. Our goal has been to monitor nvC trachomatis among our patients from January 2007 and up to July 2008.

MATERIAL AND METHODS

In this time period, all C trachomatis samples at Fürst Medical Laboratory, Norway were analyzed twice. Cobas TaqMan 48 (Roche Diagnostics) was used to detect C trachomatis in isolated DNA and real-time PCR methods developed by us were used to both detect and verify nvC trachomatis.

RESULTS

61 patients of 23 726 patients were identified as carriers of nvC trachomatis. The proportion of C trachomatis carriers who were positive for nvC trachomatis increased from 1.0 % in the first quarter of 2007 to 3.2 % in the second quarter of 2008.

INTERPRETATION

Our results show a slow but steady increase in the proportion of nvC trachomatis positive tests. As compared to previous rates reported in Sweden (25-80 %), the occurrence of nvC trachomatis in our data is low. The epidemiology of this chlamydia mutant contributes to the understanding of mechanisms for spread of sexually transmitted infections and emphasize that you only find what you are looking for.

Reference intervals for serum testosterone, SHBG, LH and FSH in males from the NORIP project

Reference intervals were calculated for male testosterone, SHBG, FSH and LH in serum from 599 individuals in the NORIP study. At 30 years of age, reference limits were calculated to 10.4-32.6 nmol/L testosterone, 13.5-57.4 nmol/L SHBG, 1.93-9.7 IU/L LH and 1.5-10.3 IU/L FSH, at 50 years, 9.3-31.3 nmol/L (testosterone), 18.4-75.6 nmol/L (SHBG), 2.01-10.4 IU/L (LH) and 2.04-12.4 IU/L (FSH), and at 70 years 8.6 to 30.7 nmol/L (testosterone), 27.8-101 nmol/L (SHBG), 2.22-11.2 IU/L (LH) and 2.71-14.2 IU/L (FSH). All age-+related changes were statistically significant. Reference intervals were also calculated for indices derived from testosterone, SHBG and albumin. Free androgen index, simply the ratio between testosterone and SHBG, returned results differing from the other elaborate indices, and the study thus favors use of a more elaborate index such as calculated free testosterone (CFT).

Heterofile antistoffer - en kilde til analyseinterferens

 Sirkulerende naturlig forekommende humane antistoffer mot humane antistoffer (rheumatoide faktorer) og mot dyreantistoffer (heterofile antistoffer) har evner til å binde analyseantistoffer som brukes i en immunometrisk analyse. Resultatet er oftest et falsk forhøyet prøvesvar (positiv interferens) og noen ganger et falsk for lavt svar (negativ interferens). Slik interferens kan reduseres betydelig gjennom modifisering av analyseantistoffene og gjennom buffertilsetninger, men forekomsten av interferens kan i dag ikke helt elimineres. Det er derfor viktig at klinikeren kjenner til risikoen for interferens, og gir laboratoriet tilbakemelding dersom prøvesvaret ikke stemmer med klinikkenHeterophilic antibodies – a source of analytical interference. Human antibodies binding human or animal antibodies may cause aberrant results in immunometric assays by binding the assay antibodies involved. The result may be falsely elevated (positive interference) or falsely low (negative interference). Both the frequency and the size of the aberrations may be reduced by either modifying the assay antibodies or by using buffer additives. However, as such interference cannot be completely eradicated, awareness of physicans and scientists is strongly needed.

Reference intervals for carcinoembryonic antigen (CEA), CA125, MUC1, Alfa-foeto-protein (AFP), neuron-specific enolase (NSE) and CA19.9 from the NORIP study

OBJECTIVE

Adhering to current IFCC recommendations, we calculated upper 97.5 % reference limits for serum tumor markers.

MATERIAL AND METHODS

Serum samples from 498 healthy individuals from the Nordic reference interval project (NORIP) were investigated for carcinoembryonic antigen (CEA), CA125 and MUC1 (episialin, CA15.3) using in-house immunofluorometric assays and, for alpha-foetoprotein (AFP), a PerkinElmer Life Sciences assay, neuron-specific enolase (NSE) using an in-house immunoradiometric assay and CA19.9 using a Beckman Access assay. All assays participate in external quality assessment programs.

RESULTS

CEA concentrations increased with age and smoking. Upper reference limits for non-smokers were 3.59 microg/L at 50 years and 4.12 microg/L at 70 years. CA125 concentrations were age-independent and the upper reference limit was 35.8 kU/L. MUC1 increased with age and body mass index (BMI). Upper reference limits were 31.7 kU/L at 40 years and BMI 24, 37.5 kU/L at 70 years and BMI 24, and 33.7 kU/L at 40 years and BMI 30. AFP increases with age, and the upper reference limits were 3.82 kU/L at 20 years and 8.70 kU/L at 60 years. An upper reference limit for NSE was 8.91 microg/L in non-smokers; smokers exhibited significantly lower levels. The upper reference limit for individuals expressing CA19.9 was 28.3 kU/L.

CONCLUSIONS

For AFP, CA125 and CA19.9, the reference levels obtained were close to previously reported reference ranges. Smoking and age were confirmed as covariates for CEA. The associations between MUC1 with age and BMI and between NSE and smoking have not been reported previously.

Progastrin-releasing peptide: stability in plasma/serum and upper reference limit

BACKGROUND

Progastrin-releasing peptide (proGRP) is a promising tumor marker for small cell lung cancer (SCLC). Here we study the stability of proGRP in serum and plasma, as well as proGRP levels in healthy individuals, to provide a framework for clinical studies.

METHODS

Serum, with and without protease inhibitors, and plasma from SCLC patients and healthy individuals were assayed for proGRP immediately after collection and following various storage conditions.

RESULTS

No degradation was observed in serum or plasma after storage for 4 weeks at -30 degrees C. Serum proGRP levels were stable for up to 3 days at 4 degrees C, but decreased at room temperature. Addition of protease inhibitors to patient serum did not markedly improve stability. In EDTA plasma, proGRP concentrations increased upon storage in some samples at room temperature and 4 degrees C. When assayed immediately after collection, no significant variations in proGRP concentrations were observed between serum and EDTA plasma (n = 171). A 97.5-percentile reference limit of 58.9 ng/l was calculated from data from 806 individuals. However, proGRP levels were significantly correlated with age, sex, creatinine concentrations, body mass index and smoking.

CONCLUSION

Serum is the preferred material for measuring proGRP, provided it is stored at 4 degrees C and assayed within 3 days.

Automated Time-Resolved Immunofluorometric Assay for Progastrin-Releasing Peptide

Background: Small cell lung cancer accounts for approximately 20% of new cases of lung cancer, and advanced disease is prevalent at the time of diagnosis. Neuron-specific enolase (NSE) has been the primary tumor marker in small cell lung cancer but it has relatively low sensitivity in early-stage disease. Progastrin-releasing peptide (proGRP) is a promising alternative or complementary marker for NSE. We have previously described a time-resolved immunofluorometric assay (TR-IFMA) for proGRP that lacked the necessary sensitivity and robustness for use in the routine clinical laboratory. Herein we describe the development of an improved assay using a novel monoclonal antibody pair.

Methods: Mice were immunized with different conjugated proGRP peptides, including residues 31–98, 1–98, and preproGRP(-23–125). Pair combinations of the resulting monoclonal antibodies (mAb) were tested. The improved TR-IFMA was compared with the only other available proGRP assay, the proGRP ELISA (IBL).

Results: A panel of 12 high-affinity mAbs was produced. The best assay combination was between our original E146 mAb as solid-phase antibody and the new mAb M16 as tracer. The new TR-IFMA had a linear dose-response curve, a wide dynamic range (13–13 500 ng/L), and a limit of detection of 2.8 ng/L. Total CV was &lt;5.6% over the whole measuring range. Bland-Altman difference analysis indicated a significant positive bias between the IFMA and the ELISA.

Conclusions: We describe a sensitive and robust mAb-based TR-IFMA for proGRP. The assay is fully automated and displays high quality performance.

Age-dependent biochemical quantities: an approach for calculating reference intervals

OBJECTIVE

A parametric method is often preferred when calculating reference intervals for biochemical quantities, as non-parametric methods are less efficient and require more observations/study subjects. Parametric methods are complicated, however, because of three commonly encountered features. First, biochemical quantities seldom display a Gaussian distribution, and there must either be a transformation procedure to obtain such a distribution or a more complex distribution has to be used. Second, biochemical quantities are often dependent on a continuous covariate, exemplified by rising serum concentrations of MUC1 (episialin, CA15.3) with increasing age. Third, outliers often exert substantial influence on parametric estimations and therefore need to be excluded before calculations are made.

MATERIAL AND METHODS

The International Federation of Clinical Chemistry (IFCC) currently recommends that confidence intervals be calculated for the reference centiles obtained. However, common statistical packages allowing for the adjustment of a continuous covariate do not make this calculation.

RESULTS

In the method described in the current study, Tukey's fence is used to eliminate outliers and two-stage transformations (modulus-exponential-normal) in order to render Gaussian distributions. Fractional polynomials are employed to model functions for mean and standard deviations dependent on a covariate, and the model is selected by maximum likelihood. Confidence intervals are calculated for the fitted centiles by combining parameter estimation and sampling uncertainties. Finally, the elimination of outliers was made dependent on covariates by reiteration.

CONCLUSIONS

Though a good knowledge of statistical theory is needed when performing the analysis, the current method is rewarding because the results are of practical use in patient care.

Use of an In Vivo Biotinylated Single-Chain Antibody as Capture Reagent in an Immunometric Assay to Decrease the Incidence of Interference from Heterophilic Antibodies

Background: Heterophilic antibodies are a common source of interference in immunometric assays. We tested the hypothesis that the incidence of such interference could be decreased by use of a recombinant in vivo-biotinylated single-chain antibody (scFv) as the capture reagent.

Methods: We established three assays for carcinoembryonic antigen (CEA) with the capture antibody either chemically biotinylated whole monoclonal T84.66 immunoglobulin, a corresponding F(ab′)2 fragment, or a site-specifically biotinylated T84.66-derived single-chain antibody (scFv). Antibodies were attached to streptavidin-coated microplates. A common europium-labeled anti-CEA tracer monoclonal antibody was used. The F(ab′)2 assay used a buffer that contained bovine immunoglobulin and aggregated irrelevant monoclonal antibody MAK33 as blocking agents. The whole T84.66 immunoglobulin and scFv assays were performed without addition of blocking agents. From a previous study of 11 261 sera, we tested 390 samples that had displayed heterophilic antibody interference and 179 samples that had not.

Results: After correction for bias and analytical variation [2.56 × SD (from the precision profile)], 383 samples displayed significantly different values (&gt;1 μg/L) in the whole T84.66-based assay and the F(ab′)2 assay. In contrast, only nine samples showed falsely high CEA concentrations in the scFv assay. After blocking agents were added to the assay buffer, eight of the nine samples displayed results equivalent to those of the F(ab′)2 assay, and sample dilution produced equivalent results for the remaining sample.

Conclusion: Their ability to be site-specifically biotinylated and their relative resistance to heterophilic antibody interference indicate that single-chain antibodies may be useful solid-phase reagents in immunometric assays.

Human heterophilic antibodies display specificity for murine IgG subclasses

OBJECTIVES

The study investigated heterophilic antibodies: the human immunoglobulin classes involved and their specificity for different murine IgG subclasses.

DESIGN AND METHODS

Using immunofluorometric assays for human IgA, IgM and IgG binding murine IgG1, we analyzed 173 samples displaying positive interference and 97 negative control samples from a previous study. We also set up assays for heterophilic antibody interference using Mabs from different murine IgG subclasses. Three Mabs each of murine IgG1, IgG2a and IgG2b subclasses, one murine IgG3 Mab and one rat Mab were used.

RESULTS

Elevated levels of human murine IgG1-binding immunoglobulins of IgM class only were found in 40% of interference-positive samples, human IgG only in 1.7%, and human IgA only in 2.3% of the samples. Both elevated human IgG and IgM classes were found in 3.5% of the samples, IgA and IgM in 4.0%, and finally, all three immunoglobulin classes in 1.7% of the samples. Eighty percent of interference positive samples showed heterophilic assay interference for at least one murine IgG1 Mab, 35% for IgG2a, 66% for IgG2b, 52% for IgG3a and 17% for the rat Mab.

CONCLUSIONS

Heterophilic antibody interference is mainly caused by IgM class human antibodies with a marked murine IgG subclass specificity. Combining assay antibodies from different murine IgG subclasses may reduce interference in immunoassays.

Testing and validating a homogeneous immunometric assay for interference

We analyzed 95 sera, demonstrating interference in a previous study, with the Kryptor homogeneous time-resolved fluorescence resonance energy transfer carcinoembryonic antigen (CEA) immunoassay (Brahms AG, Berlin, Germany). Only one serum differed, i.e., 6.0 μg/l for Kryptor vs. 13.3 μg/l for a microtiter plate in-house immunofluorometric assay (IFMA), using both aggregated mouse immunoglobulins as blocker and capture monoclonal antibody (Mab) F(ab′)

Kryptor-CEA assay results thus agreed with our inhouse CEA assay results, showing no interference. As the Kryptor-CEA assay antibodies were sensitive to interference and the Kryptor-CEA assay buffer did not reduce interference as efficiently as our in-house assay buffer, the Kryptor-CEA assay format was crucial for the absence of interference.

MUC1 serum assays in breast cancer: tumor specificities and reference levels

The aim of the study was to establish reference ranges and to explore the tumor specificities of two automated assays for MUC1. Sera from 124 female blood donors, 144 patients with benign disease of the breast, 69 patients with stage I, 75 with stage II, 89 with stage III and 38 patients with stage IV breast cancer were analyzed for MUC1 levels using two automated immunometric assays employing assay antibody pairs Ma695/Ma552 and BC2/GP1.4, respectively. All subjects were female. The Ma695/Ma552 assay yielded means of 13.86 (SD 6.55) kU/l for blood donors, 15.98 (SD 8.31) kU/l for benign disease, 15.83 (SD 7.92) kU/l for stage I, 15.01 (SD 8.03) kU/l for stage II, 33.80 (SD 66.53) kU/l for stage III and 469.22 (SD 906.61) kU/l for stage IV breast cancer. The BC2/GP1.4 assay gave means of 12.00 (SD 6.41) kU/l for blood donors, 14.68 (SD 9.33) kU/l for benign disease, 14.13 (SD 8.12) kU/l for stage I, 12.10 (SD 6.61) kU/l for stage II, 19.80 (SD 29.05) kU/l for stage III and 191.04 (SD 527.16) kU/l for stage IV breast cancer. Patients with benign diseases of the breast had slightly higher values than female blood donors with both assays leading to correspondingly different reference ranges. The Ma695/Ma552 assay had higher specificity for tumor MUC1 than the BC2/GP1.4 assay for all stages, and the study thus confirms the differences in tumor specificity for MUC1 assays.

Protein epitopes in carcinoembryonic antigen. Report of the ISOBM TD8 workshop

To characterize antigenic sites in carcinoembryonic antigen (CEA) further and to investigate whether there are differences between colon tumor CEA and meconium CEA (NCA-2) that can be detected by anti-CEA monoclonal antibodies (MAb), 19 new anti-CEA MAb were analyzed with respect to specificity, epitope reactivity and affinity. Their reactivities were compared with 10 anti-CEA MAb with known CEA-domain binding specificity that have previously been classified into five nonoverlapping epitope groups, GOLD 1-5. Cross-inhibition assays with antigen-coated microtiter plates and immunoradiometric assays were performed in almost all combinations of MAbs, using conventionally purified CEA (domain structure: N-A1B1-A2B2-A3B3-C) from liver metastasis of colorectal carcinomas, recombinant CEA, meconium CEA (NCA-2), truncated forms of CEA and NCA (CEACAM6) as the antigens. The affinity of the MAbs for CEA was also determined. The new MAbs were generally of high affinity and suitable for immunoassays. Three new MAbs were assigned to GOLD epitope group 5 (N-domain binding), 3 MAbs to group 4 (A1B1 domain), 1 to group 3 (A3B3 domain), 3 to group 2 (A2B2 domain) and 3 to group 1 (also the A3B3 domain). Three MAbs formed a separate group related to group 4, they were classified as GOLD 4' (A1B1 domain binding). The remaining 3 MAbs appear to represent new subspecificities with some relationship to GOLD groups 1, 2 or 4, respectively. Five MAbs, all belonging to epitope group 1 and 3, reacted strongly with tumor CEA but only weakly or not at all with meconium CEA, demonstrating that the two products of the CEA gene differ from each other, probably due to different posttranslational modifications.

Serum levels of soluble transferrin receptor correlate with severity of disease but not with iron stores in patients with malignant lymphomas

Soluble transferrin receptor levels in serum (s-sTfR) may be useful in differentiating between iron deficiency anemia and anemia of chronic disease. However, there is both theoretical and clinical evidence for elevated s-sTfR levels in patients with various hematological malignancies. In the present study, routine bone marrow aspirations were performed in 82 patients with malignant lymphomas (63 with non-Hodgkin's lymphoma and 19 with Hodgkin's disease). Smears were stained for evaluation of iron stores and graded. Patients were also given a disease score based on bone marrow morphology, erythrocyte sedimentation rate and LDH. s-sTfR levels correlated better with disease score [partial Spearman rank correlation coefficient (r(s)) controlled for iron stores was 0.51 (95% confidence interval 0.39-0.65); p < 0.001] than with iron stores [partial r(s) controlled for disease score was -0.25 (95% confidence interval -0.44 to -0.03); p = 0.027]. This study showed elevated s-sTfR levels in patients with malignant lymphomas without any signs of iron deficiency anemia. The diagnosis of iron deficiency anemia should not be established upon the basis of s-sTfR alone in this group of patients.

Immunometric assay interference: incidence and prevention

BACKGROUND

The primary aim of the study was to reduce interference in an in-house two-site, two-step immunometric assay.

METHODS

In the running laboratory routine, 11 261 samples were tested with a carcinoembryonic antigen (CEA) assay with bovine immunoglobulin but no murine immunoglobulins in the buffer, in parallel to our routine CEA assay, using 15 mg/L heat-treated nonspecific murine immunoglobulin (MAK33) in the buffer and with the Fc fragments removed from the capture antibody.

RESULTS

The frequency of interference was estimated to be 4.0% (95% confidence interval, 3.3-4.7%). The addition of 15 mg/L native MAK33 had little effect (frequency, 3.9%; 95% confidence interval, 3.2-4.6%), whereas adding 15 mg/L heat-treated MAK33 reduced interference to 0.86% (0.61-1.12%), and adding 50 mg/L reduced it further to 0.06% (0-0.13%). Removing the Fc fragments by itself reduced interference to 0.10% (0.02-0.19%). There were no statistically significant differences for age (P <0.23) or gender (P <0.40) between patients with interference (n = 210) and a randomly selected interference-negative control group (n = 186). Interference was not constant in patients: 15 of 25 individuals positive for interference and with four or more samples screened for interference had an interference-negative sample either before or after the peak of interference.

CONCLUSIONS

In a two-site, two-step immunometric assay using mouse monoclonal antibodies, use of heat-treated nonspecific murine immunoglobulin in the buffer or removal of the Fc fragment from the capture antibody could improve performance.

Immunometric Assay Interference

Background: The primary aim of the study was to reduce interference in an in-house two-site, two-step immunometric assay.

Methods: In the running laboratory routine, 11 261 samples were tested with a carcinoembryonic antigen (CEA) assay with bovine immunoglobulin but no murine immunoglobulins in the buffer, in parallel to our routine CEA assay, using 15 mg/L heat-treated nonspecific murine immunoglobulin (MAK33) in the buffer and with the Fc fragments removed from the capture antibody.

Results: The frequency of interference was estimated to be 4.0% (95% confidence interval, 3.3–4.7%). The addition of 15 mg/L native MAK33 had little effect (frequency, 3.9%; 95% confidence interval, 3.2–4.6%), whereas adding 15 mg/L heat-treated MAK33 reduced interference to 0.86% (0.61–1.12%), and adding 50 mg/L reduced it further to 0.06% (0–0.13%). Removing the Fc fragments by itself reduced interference to 0.10% (0.02–0.19%). There were no statistically significant differences for age (P &lt;0.23) or gender (P &lt;0.40) between patients with interference (n = 210) and a randomly selected interference-negative control group (n = 186). Interference was not constant in patients: 15 of 25 individuals positive for interference and with four or more samples screened for interference had an interference-negative sample either before or after the peak of interference.

Conclusions: In a two-site, two-step immunometric assay using mouse monoclonal antibodies, use of heat-treated nonspecific murine immunoglobulin in the buffer or removal of the Fc fragment from the capture antibody could improve performance.