Background: The aim of this study was to establish ranges for N Latex free light-chain (FLC) monoclonal-based nephelometric assays in patients with renal impairment.
Methods: In this retrospective study, serum samples from 284 patients with chronic kidney disease (CKD) stages 1–5 were measured with N Latex and Freelite™ FLC reagents on the Siemens BN™II system and compared with controls without renal impairment.
Results: Both κFLC and λFLC concentrations increased with the N Latex FLC and the Freelite™ assays with each increment in CKD stage. No difference was found in FLC κ concentrations between the two methods. In patients with renal failure, N Latex FLC detected higher concentrations of λFLC (CKD5 median, 128 mg/L; 95% range, 43–302) compared with Freelite™ (89.5 mg/L, 35–197) (p<0.0001). This resulted in significantly different κ/λ ratios in patients with CKD for the two tests. The Freelite™ κ/λ ratio in the CKD5 group (median, 1.22; min–max, 0.22–2.70) was significantly increased compared with healthy controls (p<0.0001), and several individual samples were outside the reference range for healthy controls (0.26–1.65). In contrast, none of the 284 patients with CKD had an FLC κ/λ ratio exceeding the N Latex reference limits for healthy controls (0.31–1.56). The N Latex FLC κ/λ ratio in the CKD5 group (0.69, 0.32–1.54) was significantly lower compared with the control group (p<0.0001).
Conclusions: These findings demonstrate that the N Latex FLC κ/λ ratio in patients with renal failure did not differ from the reference limits for healthy controls.
Background: New monoclonal antibody-based assays for serum-free light chains (FLC) have become available.
Methods: In a clinical study with 541 patients, the new N Latex FLC assays were compared with the Freelite™ FLC assays and immunofixation electrophoresis (IF).
Results: Comparison of the different FLC kappa (κ) assays showed a slope of 0.99 with a deviation of 5.0%, rs=0.92, for FLC lambda (λ) a slope of 1.22, deviation 13.8%, rs=0.90 and for the κ/λ ratio a slope of 0.72, deviation –4.6%, rs=0.72. The concordance for the FLC κ assays was 91%, for FLC λ 85% and κ/λ ratio 95%. The clinical sensitivity and specificity of the κ/λ ratios in the study were comparable: 60% and 99% for the N Latex FLC assay and 61% and 97% for the Freelite™ assay. In IF-FLC positive samples, the N Latex FLC κ/λ ratio scored 20/23 (87%) samples outside the reference range and Freelite™ 21/23 (91%). For IF-FLC negative samples, N Latex FLC assay κ/λ ratio scored 338/350 (97%) within the reference range and Freelite™ scored 332/350 (95%).
Conclusions: The concordance scores and the clinical sensitivity and specificity of the new N Latex FLC assays and Freelite™ assays appeared comparable, but there are some differences in measurement of concentrations between the methods.
Intake of drugs may influence the interpretation of laboratory test results. Knowledge and correct interpretation of possible drug-laboratory test interactions (DLTIs) is important for physicians, pharmacists and laboratory specialists. Laboratory results may be affected by analytical or physiological effects of medication. Failure to take into account the possible unintended influence of drug use on a laboratory test result may lead to incorrect diagnosis, incorrect treatment and unnecessary follow-up. The aim of this review is to give an overview of the literature investigating the clinical impact and use of DLTI decision support systems on laboratory test interpretation. Particular interactions were reported in a large number of articles, but they were fragmentarily described and some papers even reported contradictory findings. To provide an overview of information that clinicians and laboratory staff need to interpret test results, DLTI databases have been made by several groups. In a literature search, only four relevant studies have been found on DLTI decision support applications for laboratory test interpretation in clinical practice. These studies show a potential benefit of automated DLTI messages to physicians for the correct interpretation of laboratory test results. Physicians reported 30–100% usefulness of DLTI messages. In one study 74% of physicians sometimes even refrained from further additional examination. The benefit of decision support increases when a refined set of clinical rules is determined in cooperation with health care professionals. The prevalence of DLTIs is high in a broad range of combinations of laboratory tests and drugs and these frequently remain unrecognized.
Knowledge of possible drug-laboratory test interactions (DLTIs) is important for the interpretation of laboratory test results. Test results may be affected by physiological or analytical drug effects. Failure to recognize these interactions may lead to misinterpretation of test results, a delayed or erroneous diagnosis or unnecessary extra tests or therapy, which may harm patients.
Thousands of interactions have been reported in the literature, but are often fragmentarily described and some papers even reported contradictory findings. How can healthcare professionals become aware of all these possible interactions in their individual patients? DLTI decision support applications could be a good solution. In a literature search, only four relevant studies have been found on DLTI decision support applications in clinical practice. These studies show a potential benefit of automated DLTI messages to physicians for the interpretation of laboratory test results. All physicians reported that part of the DLTI messages were useful. In one study, 74% of physicians even sometimes refrained from further additional examination.
Summary and outlook
Unrecognized DLTIs potentially cause diagnostic errors in a large number of patients. Therefore, efforts to avoid these errors, for example with a DLTI decision support application, could tremendously improve patient outcome.