Age-adjusted D-dimer thresholds in the investigation of suspected pulmonary embolism: A retrospective evaluation in patients ages 50 and older using administrative data

Age-adjusted D-Dimer Thresholds Combined with the Modified Wells Score as a Predictor of Lower Extremity Deep Venous Thrombosis

BACKGROUND

Neurosurgical patients are at an increased risk of deep venous thrombosis (DVT), which, if not properly managed, can lead to pulmonary embolism. This study aimed to investigate the accuracy of age-adjusted D-dimer thresholds combined with the modified Wells score as a predictor for lower extremity DVT diagnosis.

METHODS

We conducted a study among patients aged >50 years with suspected lower extremity DVT in the neurosurgery intensive care unit between December 2019 and December 2020. Receiver operating characteristic curve analysis was performed to examine the diagnostic capacity of age-adjusted D-dimer combined with the modified Wells score.

RESULTS

A total of 233 participants, with an average age of 71.81 ± 12.59 years, were enrolled in the study. The mean D-dimer levels were 0.73 ± 0.39 mg/L. Among the participants, 57 (57.9%, 33 males) were diagnosed with DVT. The age-adjusted D-dimer combined with the modified Wells score had the highest area under the curve for diagnosing lower extremity DVT compared to D-dimer and age-adjusted D-dimer alone, with an AUC of 0.858. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the age-adjusted D-dimer combined with the modified Wells score for DVT diagnosis were 78.95%, 80.68%, 57%, 92.2%, and 80.26%, respectively. When analyzing subgroups, the accuracy was 79.55% for participants with cerebral hemorrhage, 81.69% for those with craniocerebral injury, 74.99% for participants with intracranial infection, and 88.89% for those with craniocerebral tumor.

CONCLUSION

The combination of the age-adjusted D-dimer thresholds with the modified Wells score might effectively predict lower extremity DVT.

Age-Adjusted D-Dimer in the Prediction of Pulmonary Embolism: Systematic Review and Meta-analysis

Background:

Pulmonary embolism (PE), depending on the severity, carries a high mortality and morbidity. Proper evaluation, especially in patients with low probability for PE, is important to avoid unnecessary diagnostic testing.

Objective:

To review the diagnostic utility of conventional versus age-adjusted D-dimer cutoff values in patients 50 years and older with suspected pulmonary embolism.

Methods:

Systematic review with univariant and bivariant meta-analysis.

Data sources:

We searched PubMed, MEDLINE, and EBSCO for studies published before September 20th, 2020. We cross checked the reference list of relevant studies that compares conventional versus age-adjusted D-dimer cutoff values in patients with suspected pulmonary embolism.

Study selection:

We included primary published studies that compared both conventional (500 µg/L) and age-adjusted (age × 10 µg/L) cutoff values in patients with non-high clinical probability for pulmonary embolism.

Results:

Nine cohorts that included 47 720 patients with non-high clinical probability were included in the meta-analysis. Both Age-adjusted D-dimer and conventional D-dimer have high sensitivity. However, conventional D-dimer has higher false positive rate than age-adjusted D-dimer.

Conclusion:

Age-adjusted D-dimer cutoffs combined with low risk clinical probability assessment ruled out PE diagnosis in suspected patients with a decreased rate of false positive tests.

Role of a new age-adjusted D-dimer cutoff value for preoperative deep venous thrombosis exclusion in elderly patients with hip fractures

Objective

This study aimed to describe the characteristics of plasma D-dimer level with increasing age and establish a new age-adjusted D-dimer cutoff value for excluding preoperative lower limb deep vein thrombosis (DVT) in elderly patients with hip fractures.

Methods

This was a retrospective study of elderly patients who presented with acute hip fracture in our institution between June 2016 and June 2019. All patients underwent D-dimer test and duplex ultrasound. Patients were divided into six 5-year-apart age groups. The optimal cutoff value for each group was calculated by using receiver operating characteristic (ROC) curves, whereby the new age-adjusted D-dimer cutoff value was determined. The sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV) were calculated and compared when different D-dimer cutoff values were applied, i.e., conventional 0.5 mg/L, previously well-established age-adjusted cutoff value (age × 0.01 mg/L) and the new age-adjusted D-dimer cutoff value herein.

Results

There were 2759 patients included, 887 males and 1872 females, with an average age of 78 years. In total, 280 patients were diagnosed with preoperative DVT. The optimal cutoff values for the six age groups were 0.715 mg/L, 1.17 mg/L, 1.62 mg/L, 1.665 mg/L, 1.69 mg/L and 1.985 mg/L, respectively, and the calculated age-adjusted coefficient was 0.02 mg/L. With this new coefficient applied, the specificity was 61%, clearly higher than those for conventional threshold (0.5 mg/L, 37%) or previously established age-adjusted D-dimer threshold (age × 0.01 mg/L, 22%). In contrast, the sensitivity was lower than that (59% vs 85% or 77%) when D-dimer threshold of 0.5 mg/L or age-adjusted cutoff value (age × 0.01 mg/L) was used. The other indexes as PPV (15%, 11% and 12%) and NPV (93%, 93% and 94%) were comparable when three different D-dimer thresholds were applied.

Conclusions

We developed a new age-adjusted D-dimer cutoff value (age × 0.02 mg/L) for a specified high-risk population of patients aged 65 years or older with hip fractures, and demonstrated the improved utility of the D-dimer test for exclusion of DVT. This formula can be considered for use in elderly hip fracture patients who meet the applicable standards as preoperative DVT screening, after its validity is confirmed by more well-evidenced studies.

Machine learning with D-dimer in the risk stratification for pulmonary embolism: a derivation and internal validation study

AIM

To develop a machine learning model to predict the diagnosis of pulmonary embolism (PE).

METHODS AND RESULTS

We undertook a derivation and internal validation study to develop a risk prediction model for use in patients being investigated for possible PE. The machine learning technique, generalized logistic regression using elastic net, was chosen following an assessment of seven machine learning techniques and on the basis that it optimized the area under the receiver operator characteristic curve (AUC) and Brier score. Models were developed both with and without the addition of D-dimer. A total of 3347 patients were included in the study of whom, 219 (6.5%) had PE. Four clinical variables (O2 saturation, previous deep venous thrombosis or PE, immobilization or surgery, and alternative diagnosis equal or more likely than PE) plus D-dimer contributed to the machine learning models. The addition of D-dimer improved the AUC by 0.16 (95% confidence interval 0.13-0.19), from 0.73 to 0.89 (0.87-0.91) and decreased the Brier score by 14% (10-18%). More could be ruled out with a higher positive likelihood ratio than by the Wells score combined with D-dimer, revised Geneva score combined with D-dimer, or the Pulmonary Embolism Rule-out Criteria score. Machine learning with D-dimer maintained a low-false-negative rate at a true-negative rate of nearly 53%, which was better performance than any of the other alternatives.

CONCLUSION

A machine learning model outperformed traditional risk scores for the risk stratification of PE in the emergency department. However, external validation is needed.

Age adjusted D-dimer cutoffs for pulmonary embolism in a geriatric population utilizing a D-dimer unit assay

BACKGROUND

Age adjusted serum d-dimer (AADD) with clinical decision rules have been utilized to rule out pulmonary embolism (PE) in low-risk patients; however, its use in the geriatric population has been questioned and the use of d-dimer unit (DDU) assay is uncommon.

OBJECTIVE

The present study aims to compare the test characteristics of the AADD (age × 5) measured in DDU with the standard cutoff (DDU < 250) and study hospital laboratory's d-dimer cutoff (DDU < 600) in geriatric patients presenting with suspected PE.

METHODS

This retrospective study enrolled patients ≥65 years old with suspected PE and d-dimer performed between January 1, 2019 and December 31, 2019 who presented to the emergency department (ED). Charts were reviewed for CTA chest and ventilation perfusion imaging results for PE. Diagnostic parameters for each cutoff were calculated for the primary outcome.

RESULTS

510 patients were included, 20 with PE. There was no significant difference between the sensitivities of AADD (100%, 95% CI: 80-100), standard cutoff (100%, 95% CI: 80-100), and hospital cutoff (90%, 95% CI: 66.9-98.2). The hospital cutoff specificity (22.7%, 95% CI: 17.1-29.3) was significantly greater than the AADD (13.4%, 95% CI: 9.1-19.2) and standard cutoff (10.8%, 95% CI: 7.0-16.3) specificities.

CONCLUSIONS

In geriatric patients presenting to the ED with suspected PE, the AADD measured in DDUs maintained sensitivity with improved specificity compared to standard cutoff. In this population, the AADD would have safely reduced imaging by 19% without missing any PEs. AADD remains a valid tool with high sensitivity and negative predictive value in ruling out PE in geriatric patients.

Association of Intravenous Radiocontrast With Kidney Function: A Regression Discontinuity Analysis

IMPORTANCE

Radiocontrast has long been thought of as nephrotoxic; however, a number of recent observational studies found no evidence of an association between intravenous contrast and kidney injury. Because these studies are at high risk of confounding and selection bias, alternative study designs are required to enable more robust evaluation of this association.

OBJECTIVE

To determine whether intravenous radiocontrast exposure is associated with clinically significant long-term kidney impairment, using a study design that permits stronger causal interpretation than existing observational research.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included all emergency department patients aged 18 years or older undergoing D-dimer testing between 2013 and 2018 in the Canadian province of Alberta. A fuzzy regression discontinuity design was used, exploiting the fact that individuals just either side of the eligibility cutoff for computed tomographic pulmonary angiogram (CTPA)-typically 500 ng/mL-have markedly different probabilities of contrast exposure, but should otherwise be similar with respect to potential confounders.

EXPOSURES

Intravenous contrast in the form of a CTPA.

MAIN OUTCOMES AND MEASURES

Estimated glomerular filtration rate (eGFR) up to 6 months following the index emergency department visit.

RESULTS

During the study period 156 028 individuals received a D-dimer test. The mean age was 53 years, 68 206 (44%) were men and 87 822 (56%) were women, and the mean baseline eGFR level was 86 mL/min/1.73 m2. Patients just above and below the CTPA eligibility cutoff were similar in terms of measured confounders. There was no evidence for an association of contrast with eGFR up to 6 months later, with a mean change in eGFR of -0.4 mL/min/1.73 m2 (95% CI, -4.9 to 4.0) associated with CTPA exposure. There was similarly no evidence for an association with need for kidney replacement therapy (risk difference [RD], 0.07%; 95% CI, -0.47% to 0.61%), mortality (RD, 0.3%; 95% CI, -2.9% to 3.2%), and acute kidney injury (RD, 4.3%; 95% CI, -2.7% to 12.9%), though the latter analysis was limited by missing data. Subgroup analyses were potentially consistent with harm among patients with diabetes (mean eGFR change -6.4 mL/min/1.73 m2; 95% CI, -15.4 to 0.2), but not among those with other reported risk factors for contrast-induced nephropathy; these analyses, however, were relatively underpowered.

CONCLUSIONS AND RELEVANCE

Using a cohort study design and analysis that permits stronger causal interpretation than existing observational research, we found no evidence for a harmful effect on kidney function of intravenous contrast administered for CTPA in an emergency setting.

Age-adjusted D-dimer cut-off levels to rule out venous thromboembolism in patients with non-high pre-test probability: Clinical performance and cost-effectiveness analysis

BACKGROUND

As aging was found to be associated with increased D-dimer levels, the question arose whether D-dimer measurement was useful in the diagnostic strategy of venous thromboembolism (VTE) in elderly patients.

AIM OF THE STUDY

To compare retrospectively the performance of six diagnostic strategies based on the three-level Wells scores and various cut-off levels for D-dimer, evaluated using the HemosIL D-Dimer HS 500 assay, in a derivation cohort of 644 outpatients with non-high pretest probability (PTP) of VTE. The clinical usefulness of the best-performing strategy was then confirmed in a multicenter validation study involving 1255 consecutive outpatients with non-high PTP.

RESULTS

The diagnostic strategy based on the age-adjusted cut-off level calculated by multiplying the patient's age by 10 above 50 years was found to perform the best in the derivation study with a better sensitivity-to-specificity ratio than the conventional strategy based on the fixed cut-off level (500 ng/ml), a higher specificity and a negative predictive value (NPV) above 99%. Such an increase in test specificity was confirmed in the validation cohort, with the NPV remaining above 99%. Taking into account the local reimbursement rates of diagnostic tests, using this strategy led to a 6.9% reduction of diagnostic costs for pulmonary embolism and a 5.1% reduction for deep vein thrombosis, as imaging tests would be avoided in a higher percentage of patients.

CONCLUSION

The diagnostic strategy of VTE based on the age-adjusted cut-off level for D-dimer in patients over 50 years was found to be safe, with NPV above 99%, and cost-effective.

The impact of using different age-adjusted cutoffs of D-dimer in the diagnosis of pulmonary thromboembolism

Background This study was conducted to evaluate the relationship of age-adjusted D-dimer value with different coefficients in diagnosis of pulmonary embolism (PE) in geriatric patients. Methods The emergency admissions of the patients aged 65 and over with suspected PE during 2018 were reviewed retrospectively. The demographic characteristics, laboratory tests and radiologic findings of computed tomography pulmonary angiogram (CTPA) or single photon emission computed tomography ventilation/perfusion scintigraphy (V/Q) were recorded. The characteristics of the patients with PE were statistically compared with the patients without PE. The specificity and sensitivity for higher cut-off levels (age × 10-15) were presented. Results PE was detected in 39.2% (n = 246) of 628 patients aged 65 years and older included in the study. The multivariate analysis revealed that higher D-dimer level (OR = 1,00011; p < 0.001) and BUN level (OR = 1.025; p = 0.013) were independent risk factors for PE diagnosis in elderly patients. Diagnostic statistics for D-dimer cut-off levels selected from ROC analysis and calculated values as 10-15 times of age showed that if the D-dimer cut-off value used is chosen higher, lower sensitivity rates are obtained. Our results also indicated that the patients with malignancy, renal failure, central PE on CTPA and PE with high probability on SPECT VQ were presented with higher D-dimer values. Conclusion Our results do not support the use of higher D-dimer cut-off levels such as 15 times the age in geriatric population. The impact of the location of PE and comorbidities on the outcomes of these patients must be clarified for determining cut-offs with higher specificity.

Effect of Using an Age-adjusted D-dimer to Assess for Pulmonary Embolism in Community Emergency Departments

BACKGROUND

The objective of this study was to evaluate the effect of changing the laboratory-reported D-dimer reference intervals to age-adjusted reference intervals on the use of advanced chest imaging and 30-day adverse events among emergency department (ED) encounters.

METHODS

A retrospective interrupted time-series analysis of ED encounters for patients > 50 years evaluated for suspected pulmonary embolism (PE) from April 2014 to April 2016. The primary outcome was use of advanced diagnostic imaging, and the secondary outcome was 30-day mortality or PE diagnosis. Secondary analyses also quantified delayed PE diagnoses pre- and postintervention. A generalized estimating equation segmented logistic regression model, adjusting for patient and facility characteristics, was used to determine changes in odds of diagnostic imaging and 30-day mortality or PE diagnoses.

RESULTS

A total of 10,534 (5,153 pre- and 5,381 postimplementation) ED encounters were included. Advanced imaging was obtained in 35.9% of pre- versus 33% of postimplementation encounters. Age-adjusted D-dimer (AADD) showed a small and nonsignificant decrease in month-to-month trends of advanced chest imaging postimplementation (odds ratio [OR] = 0.98, 95% confidence interval [CI] = 0.96 to 1.00). Use of advanced imaging in patients with D-dimer values lower than 500 ng/mL fibrinogen-equivalent units (FEU) was similar in the preintervention (5.8%) and postintervention (6.8%) periods. However, imaging was obtained in 30% of patients postintervention with a D-dimer result less than AADD reference interval , but more than the historical 500 ng/mL FEU reference interval. Implementing an AADD threshold demonstrated no change in the rate of 30-day adverse events (missed PE or mortality).

CONCLUSION

Changing the laboratory-reported D-dimer reference intervals for evaluation of PE was not associated with reduction in advanced chest imaging and did not increase 30-day adverse events. However, there was substantial noncompliance with the age-adjusted reference intervals in the postintervention period likely blunting the impact of this intervention.