Clinical laboratory investigation of a patient with an extremely high D-dimer level: A case report

Heterophilic antibodies leading to falsely positive D-dimer concentration in an adolescent

Background

We present the case of a 15-year-old adolescent with suspected pulmonary embolism and repeatedly elevated D-dimer levels.

Key Clinical Question

We aim to determine the cause for elevated D-dimer levels in a patient without venous thromboembolism.

Clinical Approach

When the D-dimer measurement was repeated with different assays, D-dimer levels were within the normal reference interval. Dilution series with assay diluent or low-affinity antibody blocking reagents either did not or only partially decreased the D-dimer value using the original reagent kit.

Conclusion

Analyses suggested the presence of interfering heterophilic antibodies in patient plasma, a known phenomenon with immunoturbidimetric D-dimer assays, which is rarely described. Prior to drawing this conclusion, the patient underwent extensive diagnostic testing, which led to uncertainty and discomfort for the health care providers, the patient, and their family.

D-dimer Testing in Pulmonary Embolism with a Focus on Potential Pitfalls: A Narrative Review

D-dimer is a multifaceted biomarker of concomitant activation of coagulation and fibrinolysis, which is routinely used for ruling out pulmonary embolism (PE) and/or deep vein thrombosis (DVT) combined with a clinical pretest probability assessment. The intended use of the tests depends largely on the assay used, and local guidance should be applied. D-dimer testing may suffer from diagnostic errors occurring throughout the pre-analytical, analytical, and post-analytical phases of the testing process. This review aims to provide an overview of D-dimer testing and its value in diagnosing PE and discusses the variables that may impact the quality of its laboratory assessment.

Falsely elevated D-dimer partially caused by heterophilic antibodies: A case report

Plasma D-dimer is a screening marker for thrombosis and hemostasis disorders. Falsely elevated D-dimer may result in misdiagnosis and potentially invasive investigations. Therefore, identifying falsely elevated D-dimer is of great value in laboratory practice. D-dimer is determined by immunoassay and vulnerable to heterophilic antibody interference. Here, we reported a case of falsely elevated D-dimer partially caused by heterophilic antibodies. Dilution test, polyethylene glycol precipitation, heterophilic blocking reagent and method comparison were used to identify the heterophilic antibody interference. All these methods, except for the heterophilic blocking reagent, revealed the existence of heterophilic antibody interference. Polyethylene glycol precipitation failed to reduce the D-dimer to its reference interval. Therefore, we conclude that the falsely elevated D-dimer is partially caused by heterophilic antibody interference.

Analytical performance of a new immunoturbidimetric D‐dimer assay and comparison with available assays

Background

The routine D‐dimer quantification to exclude venous thromboembolism has led to the development of many assays, the usefulness of which depends on their reliability and performance.

Objective

We evaluated the analytical performances of the immunoturbidimetric Yumizen G DDi 2 assay (HORIBA Medical, Montpellier, France) performed on the Yumizen G800 analyzer and compared it with other available D‐dimer assays.

Methods

Within‐run and between‐run imprecision were evaluated using low‐ and high‐level quality‐control plasma samples. Interference due to hemolysis, icterus, lipemia, rheumatoid factor (RF), or heterophilic antibodies (human antimouse antibodies [HAMAs]) was evaluated by spiking plasma samples with hemolysate, bilirubin, Intralipid, RF, or HAMAs. The measurements obtained with the different D‐dimer assays were compared using Passing‐Bablok regression analysis and Bland‐Altman plot method, using fresh citrated plasma samples collected from 66 consecutive routine patients with a wide range of D‐dimer concentrations.

Results

Within‐ and between‐run variation coefficients for the Yumizen G DDi 2 assay ranged from 1.7% to 5.8% and from 2.8% to 5.5%, respectively. Hemolysis and icterus did not have any effect up to 10 g/L hemoglobin and 300 mg/L bilirubin. Lipemia seemed to generate an underestimation of D‐dimer concentration when the Intralipid concentration was >5 g/L. RF and HAMAs did not have any effect. The Passing‐Bablok and Bland‐Altman analyses showed small differences with other available D‐dimer assays, which were more pronounced with increasing values.

Conclusions

Its analytical performances and main technical features indicate that the new Yumizen G DDi 2 assay is suitable for the rapid quantification of D‐dimer in clinical hemostasis laboratories.

Use and misuse of biomarkers and the role of D-dimer and C-reactive protein in the management of COVID-19: A post-hoc analysis of a prospective cohort study

OBJECTIVE

Coronavirus disease 2019 (COVID-19) is associated with high mortality among hospitalized patients and incurs high costs. Severe acute respiratory syndrome coronavirus 2 infection can trigger both inflammatory and thrombotic processes, and these complications can lead to a poorer prognosis. This study aimed to evaluate the association and temporal trends of D-dimer and C-reactive protein (CRP) levels with the incidence of venous thromboembolism (VTE), hospital mortality, and costs among inpatients with COVID-19.

METHODS

Data were extracted from electronic patient records and laboratory databases. Crude and adjusted associations for age, sex, number of comorbidities, Sequential Organ Failure Assessment score at admission, and D-dimer or CRP logistic regression models were used to evaluate associations.

RESULTS

Between March and June 2020, COVID-19 was documented in 3,254 inpatients. The D-dimer level ≥4,000 ng/mL fibrinogen equivalent unit (FEU) mortality odds ratio (OR) was 4.48 (adjusted OR: 1.97). The CRP level ≥220 mg/dL OR for death was 7.73 (adjusted OR: 3.93). The D-dimer level ≥4,000 ng/mL FEU VTE OR was 3.96 (adjusted OR: 3.26). The CRP level ≥220 mg/dL OR for VTE was 2.71 (adjusted OR: 1.92). All these analyses were statistically significant (p<0.001). Stratified hospital costs demonstrated a dose-response pattern. Adjusted D-dimer and CRP levels were associated with higher mortality and doubled hospital costs. In the first week, elevated D-dimer levels predicted VTE occurrence and systemic inflammatory harm, while CRP was a hospital mortality predictor.

CONCLUSION

D-dimer and CRP levels were associated with higher hospital mortality and a higher incidence of VTE. D-dimer was more strongly associated with VTE, although its discriminative ability was poor, while CRP was a stronger predictor of hospital mortality. Their use outside the usual indications should not be modified and should be discouraged.