Evaluation and analytical validation of a handheld digital refractometer for urine specific gravity measurement

Optimization and validation of metabolomics methods for feline urine and serum towards application in veterinary medicine

BACKGROUND

Metabolomics is an emerging and powerful technology that offers a comprehensive view of an organism's physiological status. Although widely applied in human medicine, it is only recently making its introduction in veterinary medicine. As a result, validated metabolomics protocols in feline medicine are lacking at the moment. Since biological interpretation of metabolomics data can be misled by the extraction method used, species and matrix-specific optimized and validated metabolomic protocols are sorely needed.

RESULTS

Systematic optimization was performed using fractional factorial experiments for both serum (n = 57) and urine (n = 24), evaluating dilution for both matrices, and aliquot and solvent volume, protein precipitation time and temperature for serum. For the targeted (n = 76) and untargeted (n = 1949) validation of serum respectively, excellent instrumental, intra-assay and inter-day precision were observed (CV ≤ 15% or 30%, respectively). Linearity deemed sufficient both targeted and untargeted (R2 ≥ 0.99 or 0.90, respectively). An appropriate targeted recovery between 70 and 130% was achieved. For the targeted (n = 69) and untargeted (n = 2348) validation of the urinary protocol, excellent instrumental and intra-assay precision were obtained (CV ≤ 15% or 30%, respectively). Subsequently, the discriminative ability of our metabolomics methods was confirmed for feline chronic kidney disease (CKD) by univariate statistics (n = 41 significant metabolites for serum, and n = 55 for urine, p-value<0.05) and validated OPLS-DA models (R2(Y) > 0.95, Q2(Y) > 0.65, p-value<0.001 for both matrices).

SIGNIFICANCE

This study is the first to present an optimized and validated wholistic metabolomics methods for feline serum and urine using ultra-high performance liquid chromatography coupled to quadrupole-Orbitrap high-resolution mass spectrometry. This robust methodology opens avenues for biomarker panel selection and a deeper understanding of feline CKD pathophysiology and other feline applications.

Long-Chain Omega-3 Fatty Acid Supplementation and Exercise-Induced Muscle Damage: EPA or DHA?

PURPOSE

Long-chain omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) may enhance recovery from exercise-induced muscle damage (EIMD). However, it is unclear if the effects are due to EPA, DHA, or both. The purpose of this investigation was to examine the effect of EPA + DHA, EPA, and DHA compared with placebo (PL) on muscular recovery.

METHODS

Thirty males were randomized to 4 g·d -1 EPA + DHA ( n = 8), EPA ( n = 8), DHA ( n = 7), or PL ( n = 7). After 7-wk supplementation, a downhill running (20 min, 70% V̇O 2max , -16% gradient) plus jumping lunges (5 × 20 reps, 2-min rest intervals) muscle damage protocol was performed. Indices of muscle damage, soreness, muscle function, and inflammation were measured at baseline and throughout recovery. The omega-3 index (O3i; %EPA + %DHA in erythrocytes) was used to track tissue EPA and DHA status.

RESULTS

After supplementation, the O3i was significantly higher than PL in all experimental groups ( P < 0.001). Leg press performance was lower in the PL group at 24 h compared with EPA ( P = 0 .019) and at 72 h for EPA ( P = 0.004) and DHA ( P = 0 .046). Compared with PL, muscle soreness was lower in the DHA ( P = 0.015) and EPA ( P = 0.027) groups at 48 h. Albeit nonsignificant, EPA + DHA tended to attenuate muscle soreness ( d = 1.37) and leg strength decrements ( d = 0.75) compared with PL. Jump performance and power metrics improved more rapidly in the EPA and DHA groups (time effects: P < 0.001). Measures of inflammation, range of motion, and muscle swelling were similar between groups ( P > 0.05).

CONCLUSIONS

Compared with PL, 4 g·d -1 of EPA or DHA for 52 d improves certain aspects of recovery from EIMD. EPA + DHA did not clearly enhance recovery. Equivalent dosing of EPA + DHA may blunt the performance effects observed in EPA or DHA alone.

Advances in testing for sample manipulation in clinical and forensic toxicology - Part A: urine samples

In many countries, adherence testing is used to monitor consumption behavior or to prove abstinence. Urine and hair are most commonly used, although other biological fluids are available. Positive test results are usually associated with serious legal or economic consequences. Therefore, various sample manipulation and adulteration strategies are used to circumvent such a positive result. In these critical review articles on sample adulteration of urine (part A) and hair samples (part B) in the context of clinical and forensic toxicology, recent trends and strategies to improve sample adulteration and manipulation testing published in the past 10 years are described and discussed. Typical manipulation and adulteration strategies include undercutting the limits of detection/cut-off by dilution, substitution, and adulteration. New or alternative strategies for detecting sample manipulation attempts can be generally divided into improved detection of established urine validity markers and direct and indirect techniques or approaches to screening for new adulteration markers. In this part A of the review article, we focused on urine samples, where the focus in recent years has been on new (in)direct substitution markers, particularly for synthetic (fake) urine. Despite various and promising advances in detecting manipulation, it remains a challenge in clinical and forensic toxicology, and simple, reliable, specific, and objective markers/techniques are still lacking, for example, for synthetic urine.

Fluid Intake and Hydration Status Among North Carolina Farmworkers: A Mixed Methods Study

BACKGROUND

Agricultural workers are disproportionately at risk for heat-related morbidity and mortality. The purpose of this study was to explore how sociocultural and occupational factors, and environmental heat stress influenced fluid intake and hydration status among Latino farmworkers working in eastern North Carolina.

METHODS

A community-informed, mixed methods research study was conducted in partnership with staff at a federally qualified health center. In summer 2020, we recruited Latino farmworkers at migrant camps. Twenty-eight male, migrant farmworkers participated in focus group discussions and 30 completed surveys and provided urine specimens. Wet bulb globe temperatures were measured in fields where workers labored. Content analysis and parametric analyses were performed. Data integration was completed using a meta-matrix.

RESULTS

Prior to work, 46.7% of farmworkers' urine specific gravity measurements indicated dehydration, which increased to 100% after work. The farmworkers spent between 2 and 7.5 hours of their day working in conditions above the recommended limits for workplace heat exposure. Farmworkers described exposure to extreme heat and inconsistent occupational policy compliance. Farmworkers expressed the opportunity to drink water but accessibility and poor water quality limited hydration. The integrated data supported congruent findings of extreme heat, few work breaks, and substandard housing.

CONCLUSION/APPLICATION TO PRACTICE

Farmworkers are dehydrated at work, placing them at higher risk for heat-related illness (HRI). By engaging with agricultural stakeholders, occupational health nurses can combine efforts and advocate for effective health and safety work policies to reduce HRIs and deaths among farmworkers. Legislation stipulating cooling and hydration practices would support safer work environments.

Comparative estimation of nitrogen in urea and its derivative products using TKN, CHNS and hand-held refractometer

In this paper, a comparative analysis between the hand-held refractometer and other methods (TKN and CHNS) was accomplished for the estimation of nitrogen percentage (N%) in urea, nano urea fertilizer, and diesel exhaust fluid (DEF) solution. In order to compare the performance of all methods/devices, the detection of N% in different concentrations of urea, nano urea, and DEF were evaluated in terms of their linearity. The most important finding of this study was that the refractometer-based device revealed a good linear coefficient up to 40% urea solution (R² = 0.99918) among other approaches, which means the estimation of N% is more close to the theoretical value. Moreover, the refractometer has detected the urea, nano urea, and DEF samples within 3 s which were quite fast as compared to other tested methods and no requirement of any chemicals during the sample preparation and analyses. Thus, the finding of this study suggests that a hand-held urea refractometer-based portable device can be used for onsite N% determination by the fertilizer and DEF manufacturing industries and their customers due to its low cost, low power requirement, reliable estimation, rapid N% detection, and its environmental suitability.

Outpatient Assessment of Mechanical Load, Heat Strain and Dehydration as Causes of Transitional Acute Kidney Injury in Endurance Trail Runners

Background: This study aimed to globally assess heat strain, dehydration, and mechanical load as acute kidney injury (AKI) indicators in amateur endurance trail athletes during a 35.3 km run. Methods: Thirty amateur experienced trail runners completed an endurance trail run (total positive ascend 1815 m). The following assessments were performed at four measurement time points (pre-, during, immediately post [-post_0h], and after 24 h of the finish of the run [-post_24h]): serum test (creatinine, blood ureic nitrogen, albumin, creatine kinase, blood ureic nitrogen: creatinine ratio, creatinine clearance, and glomerular filtration rate), mechanical load (impacts and Player Load), heat strain and dehydration (hematocrit, urine solids, body weight and urine specific gravity), pain and exertion perception (rate of perceived exertion, lumbar and bipodal, and one-leg squat pain), and urinalysis (pH, protein, glucose, erythrocytes, and urine specific gravity). Results: There were pre vs. post_0h changes in all serum biomarkers (F = 5.4–34.45, p < 0.01). The change in these biomarkers correlated with an increase in mechanical load indicators (r = 0.47–59, p < 0.05). A total of 40% and 23.4% of participants presented proteinuria and hematuria, respectively. Pain and perceived exertion increased significantly due to effort made during the endurance trail running (F = 4.2–176.4, p < 0.01). Conclusions: Endurance trail running may lead to an increase in blood and urine indicators of transitional AKI. The difference in blood and urine markers was significantly related to the mechanical load during running, suggesting potential kidney overload and cumulative mechanical load.

Reliability of Three Urine Specific Gravity Meters Measuring Brix and Urine Solutions at Different Temperatures

CONTEXT

The measurement of urine specific gravity should be performed at room temperature (20 °C) but sample temperature is not always taken in consideration.

OBJECTIVE

Evaluate the effect of sample temperature on the measurement accuracy of a digital (DIG) and optical (MAN) refractometer and a hydrometer (HYD).

DESIGN

Quantitative comparison between measurement outcomes for a reference solution (sucrose, degrees Brix) and fresh collected urine samples.

SAMPLES

Experiment 1 used a 24 Brix (°Bx) samples and experiment 2 used 33 fresh urine samples.

MAIN OUTCOME MEASURE

Urine specific gravity (USG).

RESULTS

Experiment 1 showed DIG and MAN did not differ from reference, but HYD reported lower or inconsistent values compared to Bx, while highly correlating with Bx solutions (r: > 0.89). The overall diagnostic ability of elevated USG (≥ 1.020; ≥ 1.025; ≥ 1.030) was high for all tools (AUC > 0.92). Misclassification of samples increased from 0 to 2 at 1.020 to 1 to 3 samples at cutoff 1.025 and 1.030 USG. Bland-Altman analysis showed DIG 5 °C underreports slightly without reporting bias (r: -0.344, P = 0.13); all other plots for DIG, MAN, and HYD showed considerably larger underreporting at higher concentrations (r ranging from -0.21 to -0.97 with P > .02) at all temperatures. The outcomes of experiment 2 using DIG 20°C as standard, showed only negligible differences between DIG and MAN at all temperatures, but larger differences using HYD.

CONCLUSIONS

All tools showed reporting bias when compared to °Bx solutions which can impact classification of low and high urine concentration at higher USG cutoff values, especially at a sample temperature of 37 °C.

Using elastic scattering to determination of diseases via urine samples

<abstract> <p>In diagnosing the urinary tract and related diseases, the problem of light scattering from human urine was examined on the basis of classical electromagnetic theory. Numerical calculations were made for the designed cylindrical model with the help of optical parameters in the literature obtained from the laboratory test results of urine samples. In the designed model, the changes of the scattered intensity of the light from the urine solution according to the size parameter of the particles and the angular distribution of the system (including forward, side and back scattering) in the equatorial plane were obtained, in both transverse electric (TE) and transverse magnetic (TM) of the polarization states of the light. It was observed that the molecular density changes caused by the materials in the urine sample changed primarily the optical parameters and indirectly the intensity distribution of the scattered light. Thus, with the contribution of standard data provided as a result of light scatter calculations from urine samples taken from people with normal and different diseases, it will be easier to diagnose diseases that will be encountered later.</p> </abstract>

Potential Use of Wearable Sensors to Assess Cumulative Kidney Trauma in Endurance Off-Road Running

(1) Background: This study aimed to explore wearable sensors' potential use to assess cumulative mechanical kidney trauma during endurance off-road running. (2) Methods: 18 participants (38.78 ± 10.38 years, 73.24 ± 12.6 kg, 172.17 ± 9.48 cm) ran 36 k off-road race wearing a Magnetic, Angular Rate and Gravity (MARG) sensor attached to their lower back. Impacts in g forces were recorded throughout the race using the MARG sensor. Two blood samples were collected immediately pre- and post-race: serum creatinine (sCr) and albumin (sALB). (3) Results: Sixteen impact variables were grouped using principal component analysis in four different principal components (PC) that explained 90% of the total variance. The 4th PC predicted 24% of the percentage of change (∆%) of sCr and the 3rd PC predicted the ∆% of sALB by 23%. There were pre- and post-race large changes in sCr and sALB (p ≤ 0.01) and 33% of participants met acute kidney injury diagnosis criteria. (4) Conclusions: The data related to impacts could better explain the cumulative mechanical kidney trauma during mountain running, opening a new range of possibilities using technology to better understand how the number and magnitude of the g-forces involved in off-road running could potentially affect kidney function.

Proteinuria and Bilirubinuria as Potential Risk Indicators of Acute Kidney Injury during Running in Outpatient Settings

Background and objectives: The purpose of this study was to explore which urinary markers could indicate acute kidney injury (AKI) during prolonged trail running in outpatient settings. Materials and Methods: Twenty-nine experienced trail runners (age 39.1 ± 8.8 years, weight 71.9 ± 11 kg, height 171.9 ± 8.3 cm) completed a 35 km event (cumulative positive ascend of 1815 m, altitude = 906 to 1178 m.a.s.l.) under a temperature of 25.52 ± 1.98 °C and humidity of 79.25 ± 7.45%). Two participant groups (AKI = 17 and No-AKI = 12) were made according to AKI diagnosis criteria based on pre- and post-race values of serum creatinine (sCr) (an increase of 1.5 times from baseline). Blood and urinalysis were performed immediately pre- and post-race. Results: Pre- vs. post-race differences in sCr and sBUN were found in both AKI and No-AKI groups (p < 0.01). Differences in post-race values were found between groups (p = 0.03). A total of 52% of AKI runners presented significant increases in proteinuria (χ² = 0.94, p = 0.01) and 47% in bilirubinuria (χ² = 0.94, p = 0.04). Conversely, No-AKI participants presented no significant increases in urine markers. Conclusions: These study’s findings may suggest the potential use of urinalysis as an accessible alternative in the outpatient setting to early identify transitional AKI until a clinical confirmation is performed.

Urinalysis in dog and cat: A review

Urinalysis is the examination of normal and abnormal constituents of urine. It is an easy, cheap, and vital initial diagnostic test for veterinarians. Complete urinalysis includes the examination of color, odor, turbidity, volume, pH, specific gravity, protein, glucose, ketones, blood, erythrocytes, leukocytes, epithelial cells, casts, crystal, and organisms. Semi-quantitative urine analysis with urine dipsticks, as well as an automatic analyzer, provides multiple biochemical data. Contamination is almost entirely avoided if the protocols for ensuring a proper sample have been followed, as mentioned still consideration must be given to the likelihood of contamination, even if the sample is correctly obtained. Interpretation of urinalysis will be doubtful if the knowledge of the interference is limited. Well-standardized urinalysis, when correlated in the context of history, clinical findings, and other diagnostic test results, can identify both renal and non-renal disease. This paper reviews significance of different components of urinalysis of dog and cat, such as collection, storage, examination, interpretation, and common causes of error in the result.

Intermittent Pneumatic Compression and Cold Water Immersion Effects on Physiological and Perceptual Recovery during Multi-Sports International Championship

BACKGROUND

Congested-fixture championships are common during the selection of the athletes and teams participating in the Olympic Games. Throughout these tournaments, it is fundamental to perform optimally, rest well, and recover between competitions. This study aimed to (a) explore the effectiveness of the use of intermittent pneumatic compression (IPC) and cold water immersion (CWI) to recover muscle mechanical function (MuscleMechFx), hydration status (HydS), pain perception (PainPercep), rate of perceived exertion (RPE), sleep hours, and sleep quality (SleepQual) during a regional multi-sports international championship and (b) compare these results by sex.

METHODS

A total of 52 basketball and handball players were exposed to a recovery protocol after the competition as follows: IPC, sequential 20 min at 200 mmHg, and CWI, continuous 12 min at 12 °C.

RESULTS

MuscleMechFx presented differences by match and sex (p = 0.058) in time of contraction of biceps femoris; SleepQual and sleep hours were different between matches (<0.01).

CONCLUSIONS

IPC + CWI seems to be effective to maintain some MuscleMechFx, HydS, and recovery and pain perception during a congested multi-sport tournament.

The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review

Frequent monitoring of hydration status may help to avoid the adverse effects of dehydration. Other than urine color assessment, hydration assessment methods are largely impractical for the general population and athletes to implement on a routine basis. Despite its widespread use, the validity of urine color as an indicator of hydration status has not been systematically evaluated. The objective of this systematic review is to determine the validity of urine color evaluation as a hydration status assessment method in the general adult population, older adults, and athletes. Using the PRISMA guidelines, electronic databases were searched to identify original research articles of all study design types for inclusion. Of the 424 articles screened, 10 met inclusion criteria. Most studies compared urine color to either urinary specific gravity or urine osmolality, and reported significant associations (r) ranging from 0.40 to 0.93. Lower correlations were noted in studies of adults aged >60 years. Studies generally reported a high sensitivity of urine color as a diagnostic tool for detecting dehydration and supported the ability of this method to distinguish across categories of hydration status. Research is needed to determine if clinicians, patients, and clients can accurately utilize this method in clinical and real-world settings. Future research is also needed to extend these findings to other populations, such as children.Key teaching pointsInadequate hydration can lead to impairments in physical performance and cognitive function.Methods used to assess hydration status include plasma/serum osmolality, urinary specific gravity (USG), urine osmolality (Uosm), change in body weight, urine volume, and urine color.Urine color assessment is a practical method that is routinely used in clinical, athletic, and other settings. The validity of this method has not been systemically evaluated.Available research was limited to 10 articles.Validity of this method was generally supported; however, research has not investigated the validity of this method by clinicians, patients and clients.

Validity of Digital and Manual Refractometers for Measuring Urine Specific Gravity During Field Operations: A Brief Report

INTRODUCTION

Dehydration can have an immediate negative impact on the performance of Soldiers in training or combat environments. Field expedient methods for assessing hydration status may be valuable for service members. Measurement of urine-specific gravity (USG) via refractometer is inexpensive, simple, fast, and a validated indicator of hydration status. Manual (MAN) and digital (DIG) refractometers are commonly used in laboratory settings however, digital (DIG) devices have not been validated in the field against MAN devices. The purpose of this study was to determine the validity and feasibility of using a DIG refractometer to assess USG compared to a MAN refractometer during a military field training exercise.

MATERIALS AND METHODS

Fifty-six military service members provided 672 urine samples during two 10-day field training exercises in central Texas. USG was assessed using a MAN and a DIG refractometer with cutoff value of ≥1.020 indicating hypohydration. The study received a non-human research determination.

RESULTS

The MAN measurements were strongly correlated with the DIG (r = 0.91, p < 0.0001) measurements. Bland-Altman analysis demonstrated agreement between the refractometers. The DIG displayed good sensitivity (93.9%) and specificity (85.8%) compared to the MAN.

CONCLUSION

The DIG refractometer used in this study was reliable and valid compared with a MAN device and was feasible for use in a field environment; however, the DIG refractometer tended to over overestimate hypohydration.

Clinical utility of urine specific gravity, electrical conductivity, and color as on-farm methods for evaluating urine concentration in dairy cattle

Background

Urine concentration (UC) provides clinically useful information concerning hydration status and renal function of animals.

Objectives

To characterize the clinical performance of urine specific gravity measured by optical refractometry (U_SG‐R) or Multistix‐SG urine reagent dipstick (U_SG‐D), urine electrical conductivity using an OAKTON Con 6 conductivity handheld meter (U_EC), urine color (U_Color) using a custom‐designed 8‐point color chart, and urine creatinine concentration (U_Creat) for assessing UC in dairy cattle.

Animals

20 periparturient Holstein‐Friesian cows.

Methods

Urine was obtained by perineal stimulation or urethral catheterization and urine osmolality (U_Osm, reference method), U_SG‐R, U_SG‐D, U_EC, U_Color, and U_Creat determined. Diagnostic test performance was evaluated using Spearman's rho and logistic regression to determine the area under the receiver operating curve (AUC) and optimal cut point for diagnosing hypohydration (U_Osm ≥800 mOsm/kg). P < .05 was considered significant.

Results

The best performing test for diagnosing hypohydration was U_SG‐R (AUC = 0.90) at an optimal cut point ≥1.030. The second‐best performing test was U_EC (AUC = 0.82) at a cut point of ≥23.7 mS/cm, followed by U_Creat (AUC = 0.76) at a cut point of ≥95.3 mg/dL, and U_Color (AUC = 0.74) at a cut point of ≥4 on an 8‐point scale. Urine specific gravity measured by dipstick performed poorly (AUC = 0.63).

Conclusions and Clinical Importance

U_SG‐R and U_EC provide practical and sufficiently accurate methods for measuring UC in dairy cattle. Urine color had moderate clinical utility as a no‐cost cow‐side method for assessing UC, whereas dipstick refractometry is not recommended for assessing UC.

Urinary specific gravity as an alternative for the normalisation of endocrine metabolite concentrations in giant panda (Ailuropoda melanoleuca) reproductive monitoring

Reproductive monitoring for captive breeding in giant pandas is based on behavioural observation and non-invasive hormone analysis. In urine, interpretation of results requires normalisation due to an animal’s changing hydration. Correction of urinary concentrations based on creatinine is the gold standard. In this study, a largely unexplored, easy-to-perform normalisation technique, based on urinary specific gravity (USpG), was examined and compared to creatinine. To this extent, six cycles from two female pandas (SB741(1) and SB569(5)) were monitored through urine analysis for oestrogen, progesterone, ceruloplasmin and 13,14-dihydro-15-keto-PGF2a (PGFM). The Pearson’s correlation between creatinine and USpG was high (r = 0.805–0.894; p < 0.01), indicative for a similar performance of both normalisation methods. However, generally lower values were observed during pro-oestrus and primary (progesterone) rise. This could be associated with huge shifts in appetite, monitored by faecal output (kg) with an averaged > 50% decrease during oestrus and >50% increase during primary progesterone rise. In parallel, respectively highest and lowest creatinine and USpG levels, were measured, with creatinine obviously more affected as a result of linkage with muscle tissue metabolism affected by reproductive hormones. As a consequence, metabolite levels were significantly different between both corrected datasets with significantly higher oestrogen peak levels during oestrus ranging from 2.13–86.93 and 31.61–306.45 ng/mL (USpG correction) versus 2.33–31.20 and 36.36–249.05 ng/mL Cr (creatinine correction) for SB569 and SB741 respectively, and significant lower progesterone levels during primary progesterone rise ranging from 0.35–3.21 and 0.85–6.80 ng/mL (USpG correction) versus 0.52–10.31 and 2.10–272.74 ng/mL Cr (creatinine correction) for SB569 and SB741 respectively. Consequently, USpG correction rendered unbiased profiles, less subject to variation and metabolic artefacts and therefore allowed a more straightforward identification of peak oestrogen and onset of secondary progesterone rise, being potentially advantageous for future studies unravelling key giant panda reproductive events, including (delayed) implantation. The alternative application of USpG as a normalisation factor was further supported by its easy application and environmental and technical robustness.

Clinical performance evaluation of total protein measurement by digital refractometry and characterization of non-protein solute interferences

OBJECTIVES

Refractometric methods to measure total protein (TP) in serum and plasma specimens have been replaced by automated biuret methods in virtually all routine clinical testing. A subset of laboratories, however, still report using refractometry to measure TP in conjunction with serum protein electrophoresis. The objective of this study was therefore to conduct a modern performance evaluation of a digital refractometer for TP measurement.

DESIGN AND METHODS

Performance evaluation of a MISCO Palm Abbe™ digital refractometer was conducted through device familiarization, carryover, precision, accuracy, linearity, analytical sensitivity, analytical specificity, and reference interval verification. Comparison assays included a manual refractometer and an automated biuret assay.

RESULTS

Carryover risk was eliminated using a demineralized distilled water (ddH₂O) wash step. Precision studies demonstrated overall imprecision of 2.2% CV (low TP pool) and 0.5% CV (high TP pool). Accuracy studies demonstrated correlation to both manual refractometry and the biuret method. An overall positive bias (+5.0%) was observed versus the biuret method. On average, outlier specimens had an increased triglyceride concentration. Linearity was verified using mixed dilutions of: a) low and high concentration patient pools, or b) albumin-spiked ddH₂O and high concentration patient pool. Decreased recovery was observed using ddH₂O dilutions at low TP concentrations. Significant interference was detected at high concentrations of glucose (>267 mg/dL) and triglycerides (>580 mg/dL). Current laboratory reference intervals for TP were verified.

CONCLUSIONS

Performance characteristics of this digital refractometer were validated in a clinical laboratory setting. Biuret method remains the preferred assay for TP measurement in routine clinical analyses.