Technical Note: Negative Interference of Ashwagandha, an Indian Ayurveda Medicine Indicated for Preventing COVID-19, in IL-6 Immunoassay

OBJECTIVE

Ashwagandha, an Indian Ayurvedic medicine is indicated to prevent COVID-19 infection. Because IL-6 and C-reactive protein are widely measured to determine risk of cytokine storm in hospitalized COVID-19 patients, we studied potential interference of ashwagandha on these two assays. Previous studies indicated that ashwagandha may interfere with digoxin assay, so we also studied potential interference with digoxin assay.

MATERIALS AND METHODS

We obtained one ashwagandha product from India (liquid extract) and one product from US (Herb Pharma; liquid extract). We prepared two serum pool each for IL-6, C-reactive protein and digoxin by combining appropriate left-over specimens submitted to our hospital laboratory for such tests. Then aliquots of each pools were supplemented with 10, 25 or 50 µL of ashwagandha extract followed by re-analysis for appropriate analyte and comparing values with original pool.

RESULTS

We observed negative interference of ashwagandha with IL-6 assay only (Indian product showed more negative interference) but C-reactive protein assay and digoxin assay were not affected. Negative interference of ashwagandha in IL-6 assay has not been reported before.

CONCLUSION

We conclude ashwagandha caused negative interference in IL-6 assay.

Technical Note: Bimodal Negative Interference of Biotin in Roche IL-6 Immunoassay

OBJECTIVE

Interleukin -6 (IL-6) is an important diagnostic test in COVID-19 patients to determine whether to initiate tocilizumab therapy or mechanical ventilation. We investigated potential interference of biotin in Roche IL-6 assay which utilizes biotinylated antibody.

METHODS

We prepared three serum pools from left-over specimens which showed IL-6 values over 40 pg/mL. Then aliquots of each serum pool were further supplemented with various amounts of biotin expected in patients taking biotin supplement and then IL-6 values were measured again using Roche IL-6 assay on the Cobas e411 analyzer.

RESULTS

We observed negative interference of biotin in IL-6 assay but interference was bimodal as maximum negative interference was observed with 100 ng/mL biotin but not with 1000 ng/mL. However, no interference was observed in the presence of 25 ng/mL biotin.

CONCLUSIONS

Biotin showed negative interference with IL-6 assay.

Effect of Biotin on Cardiac Troponin I and High Sensitivity Cardiac Troponin I Assays on Vista 1500 and ADVIA Centaur Analyzer

OBJECTIVE

Biotin interferes with biotinylated antibody based immunoassays. We investigated effect of biotin on conventional troponin I and two high sensitivity troponin I assays, all manufactured by Siemens.

MATERIALS AND METHODS

One high sensitivity troponin I assay (TNIH-1) was run using ADVIA Centaur analyzer. The second high sensitivity troponin I assay (TNIH-2) as well as conventional troponin I assay (CTNI) were run using Dimension Vista 1500 analyzer. We analyzed 25 specimens using CTNI, TNIH-1 and TNIH-2 assays for comparison of these assays. Moreover, serum pools prepared from additional specimens containing various amounts of troponin I were further supplemented with biotin to achieve biotin concentrations between 50 and 1000 ng/mL followed by reanalysis using CTNI, TNIH-1 and TNIH-2 assays.

RESULTS

Although both high sensitivity troponin I assays correlated well, there was a significant positive bias with TNIH-2. We observed no significant negative biotin interference at a level up to 250 ng/mL. Highest observed negative bias was 29.7%.

CONCLUSIONS

All three troponin I assays were free from biotin interferences up to a biotin concentration of 250 ng/mL.

An investigation of enzymatic creatinine interference in a patient receiving dopamine and dobutamine

BACKGROUND

A laboratory investigation was initiated after a renal failure patient had a 2.18 mg/dL decrease in serum creatinine, which was not explained through medical intervention. The investigation revealed specimens providing questionably low results had been collected from a peripherally inserted central catheter (PICC) line.

METHODS

Patient specimens and serum pools were analyzed by the Siemens Vista enzymatic creatinine measurement procedure. A simulation of the patient's infusion protocol examined potential PICC line carryover and specimen collection technique.

RESULTS

A simultaneously collected specimen set, arterial line and PICC line, yielded a difference of 1.86 mg/dL. Infusion and collection simulation studies suggested the most likely scenario was the infusion pump was not shut off while the specimen collection occurred and contaminated the specimen.

CONCLUSION

Providers should be aware of erroneously low creatinine results when administering catecholamine drugs and collecting specimens through the same catheter. The mechanism of specimen contamination is consistent with a siphoning effect from one lumen to the other during collection with the infusion pumps still running.

Modification of Jaffe's kinetic method decreases bilirubin interference: A preliminary report

The negative interference of bilirubin on serum creatinine determined by the kinetic alkaline picrate (Jaffe) reaction is the unresolved problem. Though high performance liquid chromatography and gas chromatography with mass spectroscopy have been proposed to be gold standards for creatinine estimation but they are not readily available in most of the clinical chemistry laboratories due to economic and technical constraints. Most of the present day analyzers use Jaffe's kinetic method without deproteinization. Though enzymatic methods are now routinely used as most accurate method but they are not acceptable due to cost constraints. Hence this study was planned to find out a possible solution to the problem of bilirubin interference by a minor modification in the commonly used Jaffe method so that it is amenable for use on the currently used analyzers.