Concordance between LDL-C estimated by various formulas and directly measured LDL-C

BACKGROUND

Although direct measurement of low-density lipoprotein cholesterol (LDL-C) in blood is possible, there are several formulas for its estimation. The performance and concordance of these formulas have not been evaluated in Colombia.

OBJECTIVE

To determine the concordance between LDL-C directly measured using the enzymatic technique and existing methods to calculate it.

METHODS

Study of diagnostic tests, and concordance. We analyzed complete lipid profile samples, which included direct measurement of LDL-C, from 2014 to 2022 at Hospital Universitario San Ignacio (Bogotá, Colombia). The direct LDL-C measurements were compared with estimations using the DeLong, Sampson, Friedewald, extended Martin/Hopkins, Anandaraja, and Cordova methods. Lin's concordance correlation coefficient (CCC) and Bland-Altman plots were employed, conducting subgroup analyses based on triglycerides (TG), and LDL-C levels. Kappa coefficients assessed agreement in LDL-C risk categories according to dyslipidemia guidelines.

RESULTS

A total of 2144 samples were evaluated. The formulas with the best CCC were DeLong (0.971) and Sampson (0.969), with no relevant differences. The extended Martin/Hopkins formula (0.964) and the Friedewald formula (0.964) also performed well. The Anandaraja (0.921) and Cordova (0.881) equations exhibited inferior performance. For all formulas, a decrease in concordance was observed when TG were ≥ 400 mg/dL or when LDL-C was <100 mg/dL. Most formulas demonstrated optimal agreement when assessed using risk categories according to dyslipidemia guidelines, except for Anandaraja and Cordova.

CONCLUSIONS

The DeLong, Sampson, extended Martin/Hopkins, and Friedewald formulas show the best concordance with directly measured LDL-C, so in most cases the results can be considered interchangeable. However, the Anandaraja and Cordova formulas are not recommended.

Utility of movement disorder society-unified Parkinson's disease rating scale for evaluating effect of subthalamic nucleus deep brain stimulation

Background

The Movement Disorders Society (MDS)-Unified Parkinson's Disease Rating Scale (UPDRS) is increasingly used to assess motor dysfunction before and after subthalamic nucleus deep brain stimulation (STN-DBS).

Objectives

We, therefore, investigated whether the MDS-UPDRS can detect longitudinal changes in motor function after STN-DBS in the same way as UPDRS.

Methods

We examined 21 patients with Parkinson's disease (PD) (mean age 59.2 ± 10.6 years, mean disease duration 12.0 ± 3.0 years) who underwent STN-DBS and whose motor functions were assessed by the UPDRS and MDS-UPDRS before, 3 months after, and 1 year after STN-DBS. We then evaluated the consistency between the scores of Parts II and III of the UPDRS and MDS-UPDRS during the off phase using Lin's concordance coefficient (LCC) and a Bland-Altman plot.

Results

The scores of Parts II and III of both the UPDRS and MDS-UPDRS were significantly decreased 3 months and 1 year after STN-DBS during the off phase. Scores of the UPDRS and MDS-UPDRS showed significant positive correlations before and after STN-DBS. We calculated estimated MDS-UPDRS scores from the UPDRS scores using a regression line and calculated the LCC between the MDS-UPDRS and the estimated MDS-UPDRS scores. The LCC value was 0.59-0.91, which suggests a relatively high consistency between the UPDRS and MDS-UPDRS. The Bland-Altman plot showed that differences between both scores were basically within ±1.96 standard deviations of the difference.

Conclusion

The present preliminary study indicated that the utility of the MDS-UPDRS in evaluating motor function before and after STN-DBS demonstrates its potential equivalency to the UPDRS.