False Negative D Vitamin Measurement in LC-MS/MS Method Due to Hyperlipidemia: Case Report

Intralipid as a matrix additive for evaluating hyperlipidemic postmortem blood

Postmortem whole blood samples can differ greatly in quality where hyperlipemia is a frequent variable that can influence the results of analytical methods. The aim of this study was to investigate the influence of lipemia on postmortem analysis as well as demonstrate the usage of Intralipid in comparison to pooled postmortem lipids as matrix additives for meaningful evaluation and validation of hyperlipidemic postmortem samples. Hyperlipidemic blood samples were simulated by adding different concentrations of Intralipid or pooled authentic postmortem lipids to bovine whole blood. The hyperlipidemic blood samples were spiked with 14 benzodiazepines and five sedative and antianxiety drugs (alprazolam, clonazepam, 7-aminoclonazepam, diazepam, flunitrazepam, 7-aminoflunitrazepam, hydroxyzine, lorazepam, midazolam, nitrazepam, 7-aminonitrazepam, nordazepam, oxazepam, propiomazine, dihydropropiomazine, temazepam, triazolam, zolpidem and zopiclone). Samples were prepared with liquid-liquid extraction followed by ultra-high performance liquid chromatography-mass spectrometry. The effects of lipemia on the recovery of analytes and internal standards (ISs) were evaluated to determine the effect of, and any differences between, the two additives. Lipemia was found to cause major interference when quantifying the analytes. For most analytes, the ISs could compensate for analyte losses. However, the most hydrophilic analytes (7-amino metabolites), together with the most lipophilic analytes (propiomazine and dihydropropiomazine), were greatly affected by lipemia (<50% recovery), and the IS could not compensate for analyte losses. In general, lower analyte recoveries were observed for samples with Intralipid as a lipemic additive in comparison to those containing pooled postmortem lipids. Both Intralipid and pooled postmortem lipids showed marked effects on the analytical results. Intralipid gave a good indication of the effects of lipemia and could be a useful tool for making a meaningful evaluation of hyperlipidemic postmortem samples during the method development and validation.

Lipemia in the Plasma Sample Affects Fentanyl Measurements by Means of HPLC-MS2 after Liquid-Liquid Extraction

Examination of fentanyl levels is frequently performed in certain scientific evaluations and forensic toxicology. It often involves the collection of very variable blood samples, including lipemic plasma or serum. To date, many works have reported the methods for fentanyl detection, but none of them have provided information about the impact on the assay performance caused by an excessive amount of lipids. This aspect may be, however, very important for highly lipophilic drugs like fentanyl. To address this issue, we developed the liquid chromatography method with mass spectrometry detection and utilized it to investigate the impact of lipids presence in rabbit plasma on the analytical method performance and validation. The validation procedure, conducted for normal plasma and lipemic plasma separately, resulted in good selectivity, sensitivity and linearity. The limits of detection and quantification were comparable between the two matrices, being slightly lower in normal plasma (0.005 and 0.015 µg/L) than in lipemic plasma (0.008 and 0.020 µg/L). Liquid–liquid extraction provided a low matrix effect regardless of the lipid levels in the samples (<10%), but pronounced differences were found in the recovery and accuracy. In the normal plasma, this parameter was stable and high (around 100%), but in the lipemic matrix, much more variable and less efficient results were obtained. Nevertheless, this difference had no impact on repeatability and reproducibility. In the present work, we provided reliable, convenient and sensitive method for fentanyl detection in the normal and lipemic rabbit plasma. However, construction of two separate validation curves was necessary to provide adequate results since the liquid-liquid extraction was utilized. Therefore, special attention should be paid during fentanyl quantification that involves lipemic plasma samples purified by this technique.

False Laboratory Test Result Through Colistin Interference in an Intensive Care Patient: Case Report

BACKGROUND

In blood samples taken for testing purposes during drug infusion in the intensive care unit, there is a risk of interference due to drug-reactive interaction during the analysis.

CASE REPORT

A 19-year-old female patient had undergone surgery for intracranial astrocytoma, 12 years ago. Acinetobacter baumannii was found in the blood culture and deep tracheal aspiration fluid of the patient who had a fever (39.2 °C) with a body temperature during the follow-up. The patient was started on colistin 2 * 4.5 million IU. After the colistin infusion, biochemical tests were requested to control the patient's clinical situation. CK-MB mass and ProBNP values were measured in high concentrations. Cardiology consultation was requested to evaluate the increase in the CK-MB mass and ProBNP values. The patient's ECG and echocardiography showed no abnormality. The increase in cardiac markers was neither clinically acceptable nor insignificant. There was no hemolysis in the sample or analytical error in the device. Variability in the tests was thought to be due to the interference. As the bloodletting time was questioned, it was determined that it was taken during colistin treatment. In order to determine the effect of colistin-related interference on the other tests, the laboratory was contacted and additional tests (TSH, FT4, Anti- TPO, B-HCG, Estradiol, Prolactin, CA 125, CA 15-3, CA 19-9, Vitamin B12, C-Peptide, DDimer, PTH, 25 hydroxy vitamin D, PT, INR, APTT) were conducted. During colistin treatment, in many tests, bias was detected between -75 and + 268.80%.

CONCLUSION

Clinicians should consider suspicious test results that are incompatible with the diagnosis for the possibility of erroneous measurements due to colistin interference and review the sampling processes.

Effects of Broad Spectrum Antibiotics on Measurement of Immunosuppressant Drugs

BACKGROUND

Antibiotics used parenterally can affect blood drug level measurements, as measured in diagnostic tests.

OBJECTIVE

To investigate the effect of six different antibiotics commonly used in intensive care units on tacrolimus, sirolimus, everolimus and cyclosporin A levels measured by mass spectrometry.

METHODS

Ampicillin + sulbactam (AB1, IV, 1 g), imipenem + cilastatin sodium (AB2, IV, 500 mg), piperacillin + tazobactam (AB3, 4.5 g, IV), ertapenem (AB4, IV, 1 g), meropenem trihydrate (AB5, 500 mg, IV) and ceftriaxone (AB6, 1 g, IV) antibiotics were used for the interference assay. Measurements were performed on the Shimadzu 8045 (Japan) LC-MS/MS instrument. Bias values were calculated.

RESULTS

The least affected immunosuppressant was cyclosporine A (between -6.88% and 3.40%). The most affected were everolimus and sirolimus. Ertapenem caused negative interference on the level of everolimus at the rate of -27.34% and sirolimus at the rate of -26.79%. Piperacillin + tazobactam and imipenem + cilastatin sodium caused positive interferences on sirolimus at the rate of 24.24% and 22.73%, respectively. Ampicillin + sulbactam, meropenem trihydrate and ceftriaxone affected the sirolimus levels at lower rates (-4.49%, 5.93% and 9.86%). Everolimus levels deviated at the rate of -11.21% to -16.99% due to imipenem + cilastatin sodium, meropenem trihydrate and ceftriaxone.

CONCLUSION

This study demonstrated the potential of antibiotic use affecting immunosuppressant levels. Antibiotic interference, especially in transplant patients, may cause erroneous immunosuppression, increasing the likelihood of rejection.

False Measurement of Blood Amino Acids by LC-MS/MS in a Patient Dependent on Matrix Effect after Total Parenteral Nutrition Infusion

BACKGROUND AND AIM

Although it is widely known that the total parenteral nutrition (TPN) used frequently in intensive care units has unwanted side effects, there is little known about how it interferes with the amino acid levels taken during the diagnosis of metabolic diseases. Amino acid can lead to inaccurate measurements with mass spectrometry due to its high molecular content of lipids and carbohydrates, which modifies the blood matrix. The purpose of this study was to emphasize the results of amino acid interference, measured with mass spectrometry, in patients administered with TPN.

CASE PRESENTATION

Incorrect clinical interpretation resulted in the case of a pneumonia patient with false positive and negative blood amino acid levels caused by TPN infusion. The amino acid profile had been requested to rule out an amino acid metabolic defect in the two-year-old boy who arrived at the pediatric clinic complaining of respiratory distress, tachypnea and hypoxemia. He was monitored in the intensive care unit for further investigation. The personnel who had performed phlebotomy also carried out the sampling during the TPN infusion administration. This caused the amino acid results and an incorrect interpretation. The following deviation ratios were detected: phenylalanine 102%, leucine 86%, isoleucine 106%, GABA 200%, citrulline 238%, glutamine 178%, ornithine 216%, 1- methyl-l-histidine 1471%, serine 312%, alanine 163%, glycine 355%, homocitrulline and carnosine 444%. The amino acid blood level measurements taken for diagnosis and screening in suspected metabolic disease may lead to involuntary false low or elevated results in patients administered with TPN.

CONCLUSION

This case demonstrates that TPN solutions affect the reference method of mass spectrometry measurement methods due to the concentration of ingredients. We suggest that inaccurate results can be avoided by carrying out the sampling prior to TPN infusion in patients whose plasma amino acid levels will be measured.

The Role of Interferences in the Increasing Incidence of Vitamin D Deficiency

OBJECTIVE

Lipemia is one of the causes of interference in immunoassay and LC-MS/MS methods. Increased prevalence of vitamin D deficiency in the US, where obesity is gradually increasing, raises the suspicion that high levels of fat diet and blood lipid levels interfere with vitamin D measurement results. The focus of this study was to investigate the effect of blood lipid profiles on vitamin D results and prevent the matrix effect.

MATERIAL AND METHODS

In this study, 25OH vitamin D3 (25OHD3) levels of 100 samples consecutively accepted to biochemistry laboratory regardless of age and sex were measured by the LC-MS/MS method, and each sample was restudied after 1/10 dilution. After dilution restudy, two groups were obtained-group 1 (results deviating below 20%) and group 2 (results deviating above 20%)-and the difference between the groups was investigated. There were 79 patients in group 1 and 21 patients in group 2. In our study, lipid profiles (triglyceride, total cholesterol, HDL, LDL) from the same samples of consecutive vitamin D patients were studied.

RESULTS

It was observed that the triglyceride, total cholesterol HDL, LDL, and 25OHD3 measurements of group 1 and group 2 were similar (p > 0.05). While the mean vitamin D value in the second group was 9.94 ± 7.85, the mean vitamin D value after dilution was measured as 39.23 ± 18.13 and was statistically significant. 25OHD3 concentrations of 21 patients out of 100 were found to be falsely low. Measurements were repeated to confirm the results.

CONCLUSION

The matrix effect caused by exogenous and endogenous interferences in the blood could be a hidden factor increasing the prevalence of vitamin D deficiency by causing falsely low 25OHD3 values. Suspicious results should be remeasured by a dilution study.