Evaluation of Roche Hemolysis Index for Reporting of Plasma Hemoglobin, and Considerations Regarding Hemolysis Detection in Use of Ventricular-Assist Devices

Introduction/Objective Our cardiac intensive care unit (CICU) asked the laboratory to provide plasma hemoglobin testing to monitor effects of ventricular-assist devices (VAD). Roche hemolysis index (HI) has been reported to be suitable for this purpose. Use of HI as a reportable test, however, must be validated in-house as a laboratory- developed test (LDT), according to CLIA regulations. We describe results of our evaluation, and caveats for intended use. Methods/Case Report Concentrated hemolysate was produced by osmotic lysis of packed red blood cells in water. Hemolysis in plasma was by dilution of concentrated hemolysate. Verification of HI as a measure of hemoglobin (mg/dL) used the Sigma-Aldrich spectrophotometric hemoglobin assay as a gold standard. Linearity, linear range, sensitivity, were investigated by dilution measurements; interferences by admixture experiments; reproducibility (precision, intra- and inter-assay) in each case by replicate measurements (n = 20). Results (if a Case Study enter NA) HI was confirmed to correspond to hemoglobin in mg/dL. Linearity was between 2-1000 mg/dL (r2 >0.99). Intra-assay precisions were <=2.5% (hemoglobin = 74,148 mg/dL); inter-assay precisions were <=4.9% (hemoglobin = 69,139 mg/dL). HI variability was ±2 at very low values (0-10 mg/dL). There were no interferences observed among common therapeutic drugs. Hyperlipemia (evaluated up to lipemic index (LI) = 225) and hyperbilirubinemia (evaluated up to icteric index (II) = 7) demonstrated no significant interference. Conclusion Analytically, HI exhibited acceptable performance for reporting of plasma hemoglobin. Deployment would require establishment of quality control (QC) and proficiency testing procedures for HI. Clinically, a caveat for use is that HI cannot distinguish between hemolysis in circulation vs. that due to sample collection. For the CICU, HI >10 mg/dL is characteristic of more than 20% of samples drawn in general, irrespective of use of VAD. Temporal patterns of HI must therefore be carefully evaluated in parallel with haptoglobin measurements to assist in VAD management.

​False-positive paracetamol levels in a patient with hyperbilirubinaemia: clinical perspectives

​Serum concentrations of paracetamol are measured to investigate the cause of acute hepatitis, monitor the clearance of paracetamol from the body and to determine if supratherapeutic levels warrant treatment with N-acetylcysteine (NAC). ​A 49-year-old man treated for ischaemic colitis developed worsening renal and liver function tests. As part of the investigation of hepatorenal failure, paracetamol levels were requested, which were elevated at 14 mg/L (normal <4 mg/L) resulting in treatment with NAC. Despite treatment, levels of paracetamol remained elevated and the link between hyperbilirubinemia and false-positive paracetamol levels was identified. ​Bilirubin and its by-products have intense absorbance in the ultraviolet and visible regions of the electromagnetic spectrum, causing interference in the enzymatic colorimetric assay most commonly used to measure paracetamol concentration, resulting in false-positive paracetamol levels. Laboratories correct for this interference above a predetermined bilirubin concentration, termed the Icteric Index; however, in our case this interference occurred at a lower level of hyperbilirubinaemia than previously identified as significant. This interaction was found to be more significant at lower bilirubin levels when low or no paracetamol levels were present in the serum, resulting in a change to laboratory practice and development of a ‘Sliding Scale’ approach to analysis. ​Concurrent bilirubin or Icteric Index measurement is recommended for all laboratories that use the enzymatic colorimetric assay for paracetamol measurement. Lower Icteric Index or bilirubin thresholds are required when low or no paracetamol levels are present in the serum to prevent false-positive paracetamol results. We describe a new ‘Sliding Scale’ approach to analysis, and highlight an important interaction for clinicians to be aware of.

PRE-EQC: A Proficiency Testing Program for Pre-Analytical and Analytical Monitoring Using Pooled Samples without Preservatives

Aim: External Quality Assurance (EQA) is basic requirement of a medical laboratory to assess the quality assurance and achieve the accreditation. The available EQA schemes evaluate the analytical performances of the laboratory but neither evaluate pre analytical factors nor mimic actual laboratory process. PRE-EQC has combined both performances in single scheme and assisting the participant laboratories to take appropriate corrective action and interpretations. Design: Pre-Analytical monitoring evaluates transport condition, correlation of the stability of samples and temperature, storage condition and environment of the laboratory of the participants and its effect on the results. A sample is specially prepared to estimate haemolysis, lipemic and icteric index. Clinical Biochemistry: Serum, fluoride and biological fluid (CSF exempted) samples are pooled from the routine collection of specimens. Pooled fractions are homogenized in a rotary shaker for 10 minutes. The clear samples are poured in individual double pack primary containers, which are placed between two gel packs in a “biohazard” labelled plastic bag. Temperature is recorded, kept in insulated thermocol box and sent to the destination. Urine Routine & Microalbumin, Creatinine Examination: Urine sample is stabilized using preservative. Methods: The process of sample pool to result submission has been completed within 6 days as samples are without preservative. Stability mimicking the transport, homogeneity and validation of assigned values were done. Statistical Calculations: As per ISO 13528:2015. Results and Discussion: The SD of the assigned values showed better performance than existing schemes and within the range of CLIA recommended SD. Conclusion: The PRE-EQC sample from direct and microalbumin from direct specimen has achieved good reproducibility than lyophilized material.