Enzyme-linked Immunosorbent Immunoassay Research Articles

BLOOD ANTI-SURFACE PROTEINS ECHOVIRUS 30 (ENTEROVIRUS, PICORNAVIRIDAE) ANTIBODIES IN RESIDENTS OF THE NIZHNY NOVGOROD REGION

Abstract Echovirus 30 (Е30) is an enterovirus that causes severe forms of serous meningitis. Over many years, E30 virus has caused serous meningitis outbreaks all over the world including Russia, but the status of anti-E30 population immunity remains unexplored. In 2022, the average percentage of all pediatric admission enterovirus cases in Russia was 97%; the most severe E30 infection cases were registered in children under 17 years of age. The virus capsid surface contains proteins VP1, VP2 and VP3 with homologous epitopes common to other enterovirus proteins, which allows them to be used as an antigen for antibody detection. The work was aimed at assessing frequency of different antibody classes specific to full-length recombinant E30 VP1, VP2 and VP3 proteins. 331 blood serum samples collected from 2 months-to 61 year-old residents of the Nizhny Novgorod region were used in the study. E30 VP1, VP2 and VP3 proteins were expressed in Escherichia coli, purified chromatographically and used antigenically for detection of IgA, IgG and IgM antibodies by using enzyme-linked immunosorbent immunoassay. Most study subjects had antibodies specific to only one or two of the E30 surface proteins. IgA, IgG and IgM antibodies to three recombinant proteins were detected simultaneously in 0.3%, 4.2% and 2.7% of cases. Totally, anti-E30 protein IgG antibodies were detected in 29.9% of cases. The maximum detection rate of antibodies (50.0%) was recorded in pediatric groups that decreased with age. IgG antibodies were found in 9.3% of the tested individuals. The detection rate (16.6%) peaked in the age group of children from 7 to 11 years. The IgM antibody-obtained data evidence that during the study period, almost one in every ten-study participant was infected with enteroviruses. The results of analyzing long-term immunity specific to enteroviral proteins showed the highest frequency of detected IgG antibodies in children that tended to decline with age as well as about continued E30 virus circulation in the Nizhny Novgorod region.

Alteration in Melanin Content in Retinal Pigment Epithelial Cells upon Hydroquinone Exposure

Abnormal pigmentation or depigmentation of the retinal pigment epithelium (RPE) is a precursor to neovascular age-related macular degeneration (nAMD). In this study, we evaluated the effects of hydroquinone (HQ), the most potent reductant in cigarette smoke, on the melanin production in RPE cells. Induced pluripotent stem cell (iPS)-derived RPE and adult retinal pigment epithelial (ARPE-19) cells were cultured with HQ. Real-time reverse transcription polymerase chain reaction revealed that the expression of melanin-related genes decreased due to the addition of HQ for 1 day. Enzyme-linked immunosorbent immunoassay showed that the concentration of melanin significantly decreased due to the addition of HQ for 24 h. A suspension of RPE cells with HQ for 24 h was prepared, and the absorbance was measured. The absorbance decreased particularly under blue light, suggesting that blue light may reach the choroid and cause choroidal inflammation. Additionally, melanin levels significantly decreased due to the addition of HQ for 1 week. After blue light irradiation on the RPE with HQ for 1 week, the vascular endothelial growth factor in the medium was significantly higher in the HQ group than in the control group. HQ-induced changes in melanin production may be responsible for the uneven pigmentation of the RPE, and these changes may cause nAMD.

Reducing the burden of surveillance in pregnant women with no history of fetal atrioventricular block using the negative predictive value of anti-Ro/SSA antibody titers

The risk of fetal atrioventricular block in anti-Ro/SSA antibody-exposed pregnancies with no previous affected offspring is approximately 2%. A high antibody titer is necessary but not sufficient for atrioventricular block, and specific antibody titers do not predict risk. However, there are no data on the negative predictive value of antibody titer to identify pregnancies at low risk of fetal atrioventricular block, and may not require surveillance. This study aimed to define anti-Ro52 and anti-Ro60 antibody thresholds for the identification of fetuses unlikely to develop atrioventricular block using clinically validated and research laboratory tests. This study performed a multicenter review of pregnant subjects who tested positive in their local commercial laboratories for anti-Ro/SSA antibodies at the University of Colorado Children's Hospital (2014-2021) and Phoenix Children's Hospital (2014-2021) and enrolled in the Research Registry for Neonatal Lupus (RRNL) at New York University Langone Medical Center (2002-2021). The subjects were referred on the basis of rheumatologic symptoms or history of atrioventricular block in a previous pregnancy and were retrospectively grouped on the basis of pregnancy outcome. Group 1 indicated no fetal atrioventricular block in current or past pregnancies; group 2 indicated fetal atrioventricular block in the current pregnancy; and group 3 indicated normal current pregnancy but with fetal atrioventricular block in a previous pregnancy. Maternal sera were analyzed for anti-Ro52 and anti-Ro60 antibodies using a clinically validated multiplex bead assay (Associated Regional and University Pathologists Laboratories, Salt Lake City, UT) and a research enzyme-linked immunosorbent immunoassay (New York University). This study calculated the negative predictive value separately for anti-Ro52 and anti-Ro60 antibodies and for the 2 combined using a logistic regression model and a parallel testing strategy. This study recruited 270 subjects (141 in group 1, 66 in group 2, and 63 in group 3). Of note, 89 subjects in group 1 had data on hydroxychloroquine treatment: anti-Ro/SSA antibody titers were no different between those treated (n=46) and untreated (n=43). Mean anti-Ro52 and anti-Ro60 titers were the lowest in group 1 and not different between groups 2 and 3. No case of fetal atrioventricular block developed among subjects with anti-Ro52 and anti-Ro60 titers of <110 arbitrary units per milliliter using the multiplex bead assay of the Associated Regional and University Pathologists Laboratories (n=141). No case of fetal atrioventricular block developed among subjects with research laboratory anti-Ro52 titers of <650 and anti-Ro60 of <4060 enzyme-linked immunosorbent immunoassay units (n=94). Using these 100% negative predictive value thresholds, more than 50% of the anti-Ro/SSA antibody pregnancies that ultimately had no fetal atrioventricular block could be excluded from surveillance based on clinical and research titers, respectively. Study data suggested that there is a clinical immunoassay level of maternal anti-Ro/SSA antibodies below which the pregnancy is at low risk of fetal atrioventricular block. This study speculated that prospectively applying these data may avert the costly serial echocardiograms currently recommended for all anti-Ro/SSA-antibody positive pregnancies and guide future management.

P133 Point-of-care measurement of infliximab and adalimumab trough levels by the fluorescence resonance energy transfer (FRET) assay

Abstract Background Therapeutic drug monitoring (TDM) is the clinical practice of measuring serum drug concentrations to guide clinical decision-making. In IBD patients, it is applied mainly in infliximab (IFX) and adalimumab (ADL) therapy. TDM is either performed reactively in response to disease activity, or proactively in the absence of symptoms. The aim of the present study was to compare two analytical methods for the detection of trough infliximab and adalimumab levels (TL): point-of-care (POCT) fluorescence resonance energy transfer (FRET) method, and the enzyme- linked immunosorbent immunoassay (ELISA). Methods TL IFX were measured in n=24 and TL ADL in n= 21 blood samples. For ELISA, standard peripheral venous samples were used, and for POCT FRET measurements, capillary finger puncture was performed. Two assay results were compared evaluating the regression relationship using Spearman’s correlation coefficient and the Bland-Altman plots. Cohen’s kappa analysis was used to compare the degree of qualitative agreement between the two data sets. Repeatability was assessed by the difference of the repeated measurements, their means and standard deviations. Results The high degree of correlation was found between the measured values, both qualitative and quantitative (p &amp;lt; 0.0001 for both IFX and ADL), either expressed by the Spearman’s correlations, or by Bland-Altman analysis. Cohen’s weighted kappa 0.903 for IFX and 0.834 for ADL showed substantial/almost perfect agreement of qualitative results. Closeness of the agreement of successive measurements was very acceptable for both TLs of both drugs. Conclusion Point-of-care detection of IFX and ADL trough levels by FRET is accurate, comparable to the reference method, analysis is sufficiently consistent. For clinical sites with a proactive approach to TDM, FRET may be a useful tool for decision-making regarding individualization of biologic therapy. Acknowledgements: We thank ProciseDX company for the ProciseDX analyzer rental, and for providing the laboratory diagnostics.

Peptidyl Arginine Deiminase Type 4 Gene Promoter Hypo-Methylation in Rheumatoid Arthritis.

Protein citrullination is carried out by peptidylarginine deiminase type 4 (PAD4) enzyme. As a consequence of this process, post-translationally modified proteins are formed that become antigens for anti-citrullinated protein antibodies (ACPA). The study aimed at identifying whether the PADI4 gene is subject to epigenetic regulation through methylation of its promoter region, whether the degree of methylation differs in healthy individuals vs. rheumatoid arthritis (RA) patients and changes in correlation with ACPA, anti-PAD4 and disease activity. A total of 125 RA patients and 30 healthy controls were enrolled. Quantitative real-time methylation-specific PCR was used to analyze the methylation status. ACPA and anti-PAD4 antibodies were determined in serum by enzyme-linked immunosorbent immunoassay. The differences were observed in the degree of PADI4 gene promoter methylation between RA patients and HC, along with an upward trend for the methylation in RA, which was inversely proportional to the disease activity. A weak or modest negative correlation between the degree of PADI4 gene methylation and anti-PAD4, disease activity score (DAS28) and ACPA level has been found. The elevated methylation is associated with lower disease activity, lower levels of ACPA and aPAD4. The methylation degree in this area is growing up during effective treatment and might play a role in the RA pathophysiology and therefore could be a future therapeutic target.

A sensitive electrochemical aptasensor for multiplex antibiotics detection based on high-capacity magnetic hollow porous nanotracers coupling exonuclease-assisted cascade target recycling

A multiplex electrochemical aptasensor was developed for simultaneous detection of two antibiotics such as chloramphenicol (CAP) and oxytetracycline (OTC), and high-capacity magnetic hollow porous nanotracers coupling exonuclease-assisted target recycling was used to improve sensitivity. The cascade amplification process consists of the exonuclease-assisted target recycling amplification and metal ions encoded magnetic hollow porous nanoparticles (MHPs) to produce voltammetry signals. Upon the specific recognition of aptamers to targets (CAP and OTC), exonuclease I (Exo I) selectively digested the aptamers which were bound with CAP and OTC, then the released CAP and OTC participated new cycling to produce more single DNA, which can act as trigger strands to hybrid with nanotracers to generate further signal amplification. MHPs were used as carriers to load more amounts of metal ions and coupling with Exo I assisted cascade target recycling can amplify the signal for about 12 folds compared with silica based nanotracers. Owing to the dual signal amplification, the linear range between signals and the concentrations of CAP and OTC were obtained in the range of 0.0005-50 ng mL(-1). The detection limits of CAP and OTC were 0.15 and 0.10 ng mL(-1) (S/N=3) which is more than 2 orders lower than commercial enzyme-linked immunosorbent immunoassay (ELISA) method, respectively. The proposed method was successfully applied to simultaneously detection of CAP and OTC in milk samples. Besides, this aptasensor can be applied to other antibiotics detection by changing the corresponding aptamer. The whole scheme is facile, selective and sensitive enough for antibiotics screening in food safety.

Development of a highly sensitive and specific immunoassay for enrofloxacin based on heterologous coating haptens

In the paper, an enzyme-linked immunosorbent immunoassay (ELISA) for detection of enrofloxacin was described using one new derivative of enrofloxacin as coating hapten, resulting in surprisingly high sensitivity and specificity. Incorporation of aminobutyric acid (AA) in the new derivative of enrofloxacin had decreased the IC50 of the ELISA for enrofloxacin from 1.3 μg L(-1) to as low as 0.07 μg L(-1). The assay showed neglect cross-reactivity for other fluoroquinolones but ofloxacin (8.23%), marbofloxacin (8.97%) and pefloxacin (7.29%). Analysis of enrofloxacin fortified chicken muscle showed average recoveries from 81 to 115%. The high sensitivity and specificity of the assay makes it a suitable screening method for the determination of low levels of enrofloxacin in chicken muscle without clean-up step.

Changes in NT-proBNP in Young Children With Congenital Heart Malformations

We measured serum NT-proBNP levels in 2 groups of young patients (0-36 months) with congestive heart failure (CHF) secondary to congenital heart malformations (CHM). The first group included 23 patients prior to surgery for heart malformations. The second group included 12 patients with CHM within 24 hours post-operation. NT-proBNP levels were measured by an enzyme-linked immunosorbent immunoassay (ELISA) using the Chem Well 2910 (Awareness Technology Inc.) automated analyzer. NT-proBNP values were 4 times higher in patients with unoperated CHM compared to healthy controls (P < 0.001), and 12 times higher in patients with CHM 24 hours after surgery compared to controls (P = 0.0001). These results demonstrated significant changes in NT-proBNP concentrations before and after surgery to correct congenital heart malformations.

Comparison between electrochemical ELISA and spectrophotometric ELISA for the detection of dentine sialophosphoprotein for root resorption

Root resorption is an undesirable sequela of orthodontic treatment. It is necessary to establish sensitive methods for identification of teeth at risk for resorption. The x-ray is the traditional method to diagnose root resorption, which is often at a late stage. Some researchers used enzyme-linked immunosorbent immunoassay (ELISA) combined with spectrophotometry to study some biochemical markers of root resorption. However, spectrophotometric detection often has a poor detection limit. Electrochemical detection has inherent advantages over spectrophotometric detection, which is especially suitable for small biologic samples. We used ELISA combined with electrochemistry and ELISA combined with spectrophotometry to measure the biochemical marker dentine sialophosphoprotein in gingival crevicular fluid of orthodontic patients (treated for 8-12 months). Standard dentine sialophosphoprotein was used to calculate the linear regression equation. No significant difference was found between the electrochemical outcome and the spectrophotometric outcome. But the electrochemical results extended the lower end of detection from 5 pg per milliliter (by spectrophotometry) to 0.5 pg per milliliter. These results showed that ELISA combined with electrochemistry is a reliable and sensitive method to detect dentine sialophosphoprotein in gingival crevicular fluid.

Forcing immunoassay for sulfonamides to higher sensitivity and broader detection spectrum by site heterologous hapten inducing affinity improvement

Three immunizing haptens, 6-(4-aminophenylsulfonamido)hexanoic acid (HS), 4-(4-(4-aminophenylsulfonamido)phenylsulfonamido)benzoic acid (SSS) and 4-(4-(4-aminophenylsulfonamido)phenyl)butanoic acid (SA10), were synthesized and used as haptens to produce generic polyclonal antibodies against sulfonamides. A novel generic enzyme-linked immunosorbent immunoassay (ELISA) for the detection of sulfonamides was developed based on one site heterologous coating hapten derived from sulfadiazine (STZ), providing IC50 values below 100 ng mL−1 for the 26 sulfonamides tested in buffer. The study showed that the site heterologous coating hapten could significantly improve the sensitivity of ELISA in comparison to a homologous or bridge length heterologous coating hapten. The developed ELISA was used first for the detection of five sulfonamides in spiked chicken muscle with recovery values ranging from 80.9 to 87.4% when the clean-up step was not included and from 85.6% to 92.7% when the clean-up step was included in sample pretreatment. The study showed that the high sensitivity and broad specificity of the assay make it a suitable screening method for the determination of multi-sulfonamides residues in chicken muscle.

Comparison of 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide Based Strategies to Crosslink Antibodies on Amine-Functionalized Platforms for Immunodiagnostic Applications.

1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) alone, and in combination with N-hydroxysuccinimide (NHS) or sulfoNHS were employed for crosslinking anti-human fetuin A (HFA) antibodies on 3-aminopropyltriethoxysilane (APTES)-functionalized surface plasmon resonance (SPR) gold chip and 96-well microtiter plate. The SPR immunoassay and sandwich enzyme linked immunosorbent immunoassay (ELISA) for HFA clearly demonstrated that EDC crosslinks anti-HFA antibodies to APTES-functionalized bioanalytical platforms more efficiently than EDC/NHS and EDC/sulfoNHS at a normal pH of 7.4. Similar results were obtained by sandwich ELISAs for human Lipocalin-2 and human albumin, and direct ELISA for horseradish peroxidase. The more efficient crosslinking of antibodies by EDC to the APTES-functionalized platforms increased the cost-effectiveness and analytical performance of our immunoassays. This study will be of wide interest to researchers developing immunoassays on APTES-functionalized platforms that are being widely used in biomedical diagnostics, biosensors, lab-on-a-chip and point-of-care-devices. It stresses a critical need of an intensive investigation into the mechanisms of EDC-based amine-carboxyl coupling under various experimental conditions.

Microcystin kinetics (bioaccumulation and elimination) and biochemical responses in common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix) exposed to toxic cyanobacterial blooms

Two species of common edible fish, common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix), were exposed to a Microcystis spp.-dominated natural cyanobacterial water bloom for two months (concentrations of cyanobacterial toxin microcystin, 182-539 microg/g biomass dry wt). Toxins accumulated up to 1.4 to 29 ng/g fresh weight and 3.3 to 19 ng/g in the muscle of silver carp and common carp, respectively, as determined by enzyme-linked immunosorbent immunoassay. Concentrations an order of magnitude higher were detected in hepatopancreas (up to 226 ng/g in silver carp), with a peak after the initial four weeks. Calculated bioconcentration factors ranged from 0.6 to 1.7 for muscle and from 7.3 to 13.3 for hepatopancreas. Microcystins were completely eliminated within one to two weeks from both muscle and hepatopancreas after the transfer of fish with accumulated toxins to clean water. Mean estimated elimination half-lives ranged from 0.7 d in silver carp muscle to 8.4 d in common carp liver. The present study also showed significant modulations of several biochemical markers in hepatopancreas of fish exposed to cyanobacteria. Levels of glutathione and catalytic activities of glutathione S-transferase and glutathione reductase were induced in both species, indicating oxidative stress and enhanced detoxification processes. Calculation of hazard indexes using conservative U.S. Environmental Protection Agency methodology indicated rather low risks of microcystins accumulated in edible fish, but several uncertainties should be explored.

Detection of the Marijuana Metabolite 11-Nor- 9-Tetrahydrocannabinol-9-Carboxylic Acid in Oral Fluid Specimens and Its Contribution to Positive Results in Screening Assays

The detection of the marijuana metabolite 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) in oral fluid specimens is described, and its contribution to an immunoassay for the detection of cannabinoids is investigated. Oral fluid specimens, screened using an enzyme-linked immunosorbent immunoassay (ELISA), were carried forward to confirmation for both tetrahydrocannabinol (THC) and THC-COOH using gas chromatography-mass spectrometry (GC-MS). One hundred and fifty-three specimens were analyzed, of which 143 screened positive for cannabinoids. Ninety-five (66.4%) of these specimens were positive for both THC and THC-COOH; 14 (9.7%) were positive for THC-COOH only, and 27 (18.8%) were positive for THC only. The GC-MS assay for the detection of THC-COOH in oral fluid was linear to 160 pg/mL with a limit of quantitation of 2 pg/mL. The detection of the marijuana metabolite, THC-COOH, in 76.2% of oral fluid specimens screening positive for cannabinoids is reported. As a potential defense against passive exposure claims, proposed SAMHSA regulations may require the simultaneous collection of a urine sample when oral fluid samples are used. The detection of the metabolite, THC-COOH, is a significant alternative to this approach because its presence in oral fluid minimizes the argument for passive exposure to marijuana in drug testing cases.

Expansion of CD14+CD16+ Blood Monocytes in Patients with Chronic Renal Failure Undergoing Dialysis: Possible Involvement of Macrophage Colony-Stimulating Factor

A novel subpopulation of blood monocytes coexpressing CD16 antigen and low levels of CD14 antigen (CD14+CD16+ monocytes) has recently been identified, and expansion of these CD14+CD16+ monocytes has been reported under some pathological conditions. In this study, we examined the immunophenotype of blood monocytes in patients with chronic renal failure (CRF) who were undergoing hemodialysis (HD, n = 52) or continuous ambulatory peritoneal dialysis (CAPD, n = 36) using two-color immunofluorescence flow cytometry. The percentage and absolute number of CD14+CD16+ monocytes were significantly higher (p < 0.001) in both HD and CAPD patients compared with those in healthy control subjects. We also determined the plasma concentrations of hematopoietic growth factors and cytokines using an enzyme-linked immunosorbent immunoassay. The plasma levels of macrophage colony-stimulating factor (M-CSF) were markedly increased in both HD and CAPD patients relative to the normal controls. The plasma M-CSF levels correlated significantly with the number of CD14+CD16+ monocytes in the whole group of subjects. These findings suggest that elevated endogenous M-CSF levels may participate in the expansion of CD14+CD16+ monocytes in CRF patients undergoing dialysis.

Production and partial characterization of monoclonal antibodies specific to cooked poultry meat

Monoclonal antibodies (MAbs) specific to cooked poultry muscle proteins have been developed for the detection of poultry adulterants in cooked mammalian meat. Saline (0.85% NaCl) extract of heat-treated (100 °C, 15min) chicken muscle proteins was used to immunize mice for MAb development. The specificity of MAbs was tested against chicken antigen and protein extracts from seven other meat species (pork, beef, lamb, deer, horse, turkey and duck) by indirect enzyme-linked immunosorbent immunoassay (ELISA). The immunogenic components in the poultry protein extracts were determined by SDS-PAGE followed by immunoblotting. A total of six hybridoma cell lines that secrete IgG class MAbs have been developed: MAbs 3E12 and 1A5 were able to distinguish between cooked poultry and mammalian meats, MAbs 9C6 and 6F7 reacted strongly with cooked chicken only, and MAbs, 5D2 and 6G8, reacted with both cooked turkey and chicken but not other species. All six MAbs demonstrated a proportional increased ELISA response to respective adulterated poultry samples in pork over a 0-100% range of aduleration.

Thrombus precursor protein (TpP): marker of thrombosis early in the pathogenesis of myocardial infarction

We have developed an enzyme-linked immunosorbent immunoassay for quantifying the immediate precursor proteins to intravascular thrombi. This thrombus precursor protein (TpP) assay identifies active thrombosis in several clinical conditions, including early myocardial infarction (MI). In a study of patients recruited for the GUSTO intervention study, MI patients had concentrations of TpP 4-20-fold that of controls; patients diagnosed without MI had concentrations similar to the control subjects. In a separate study of subjects presenting at the emergency room with chest pain, MI patients who presented early after the onset of chest pain had TpP concentrations significantly (P <0.01) higher than controls. Patients presenting late or diagnosed with other chest pain had concentrations within the reference range. The potential utility of the TpP assay as an aid for the diagnosis of thrombotic MI and other thrombotic conditions is described.

Applications of an enzyme immunoassay for a new marker of bone resorption (CrossLaps): follow-up on hormone replacement therapy and osteoporosis risk assessment.

An enzyme-linked immunosorbent immunoassay (ELISA) for a new marker of bone resorption (CrossLaps) was evaluated. The ELISA procedure determines degradation products of type I collagen in urine. Values obtained in the ELISA and in pyridinoline by high pressure liquid chromatography were correlated after a correction for creatinine. A high correlation was found (r = 0.77; n = 81). A group of postmenopausal women (n = 180) showed an increase of more than 70% compared to values in premenopausal women (n = 104). Hydroxyproline was increased by 23%, osteocalcin by 52%, pyridinoline by 31%, and deoxypyridinoline by 50%. A highly significant decrease (60.7%) in the CrossLaps values was seen after 12 months in samples from patients receiving hormone replacement therapy compared to a placebo group. The spontaneous bone loss in an untreated group of women was determined by repeated forearm bone mass measurement over 24 months. Baseline values obtained in the CrossLaps ELISA were correlated to the rate of loss, yielding a highly significant r value of -0.61, indicating that CrossLaps might be a useful parameter for assessment of the risk of osteoporosis in postmenopausal women.

Serum Immunoreactive Pancreatic Lipase and Cationic Trypsinogen for the Assessment of Exocrine Pancreatic Function in Older Patients With Cystic Fibrosis

Indirect and qualitative tests of pancreatic function are commonly used to screen patients with cystic fibrosis for pancreatic insufficiency. In an attempt to develop a more quantitative assessment, we compared the usefulness of measuring serum pancreatic lipase using a newly developed enzyme-linked immunosorbent immunoassay with that of cationic trypsinogen using a radioimmunoassay in the assessment of exocrine pancreatic function in patients with cystic fibrosis. Previously, we have shown neither lipase nor trypsinogen to be of use in assessing pancreatic function prior to 5 years of age because the majority of patients with cystic fibrosis in early infancy have elevated serum levels regardless of pancreatic function. Therefore, we studied 77 patients with cystic fibrosis older than 5 years of age, 41 with steatorrhea and 36 without steatorrhea. In addition, 28 of 77 patients consented to undergo a quantitative pancreatic stimulation test. There was a significant difference between the steatorrheic and nonsteatorrheic patients with the steatorrheic group having lower lipase and trypsinogen values than the nonsteatorrheic group (P less than .001). Sensitivities and specificities in detecting steatorrhea were 95% and 86%, respectively, for lipase and 93% and 92%, respectively, for trypsinogen. No correlations were found between the serum levels of lipase and trypsinogen and their respective duodenal concentrations because of abnormally high serum levels of both enzymes found in some nonsteatorrheic patients. We conclude from this study that both serum lipase and trypsinogen levels accurately detect steatorrhea in patients with cystic fibrosis who are older than 5 years but are imprecise indicators of specific pancreatic exocrine function above the level needed for normal fat absorption.(ABSTRACT TRUNCATED AT 250 WORDS)