Annals of Clinical Biochemistry: International Journal of Laboratory Medicine

Three multicentre studies of reference intervals were conducted recently in Japan. The Committee on Common Reference Intervals of the Japan Society of Clinical Chemistry sought to establish common reference intervals for 40 laboratory tests which were measured in common in the three studies and regarded as well harmonized in Japan.

The study protocols were comparable with recruitment mostly from hospital workers with body mass index ≤28 and no medications. Age and sex distributions were made equal to obtain a final data size of 6345 individuals. Between-subgroup differences were expressed as the SD ratio (between-subgroup SD divided by SD representing the reference interval). Between-study differences were all within acceptable levels, and thus the three datasets were merged.

By adopting SD ratio ≥0.50 as a guide, sex-specific reference intervals were necessary for 12 assays. Age-specific reference intervals for females partitioned at age 45 were required for five analytes. The reference intervals derived by the parametric method resulted in appreciable narrowing of the ranges by applying the latent abnormal values exclusion method in 10 items which were closely associated with prevalent disorders among healthy individuals. Sex- and age-related profiles of reference values, derived from individuals with no abnormal results in major tests, showed peculiar patterns specific to each analyte.

Common reference intervals for nationwide use were developed for 40 major tests, based on three multicentre studies by advanced statistical methods. Sex- and age-related profiles of reference values are of great relevance not only for interpreting test results, but for applying clinical decision limits specified in various clinical guidelines.

Plasma amino acid concentrations vary with various diseases. Although reference intervals are useful in daily clinical practice, no reference intervals have been reported for plasma amino acids in a large Japanese population.

Reference individuals were selected from 7685 subjects examined with the Japanese Ningen Dock in 2008. A total of 1890 individuals were selected based on exclusion criteria, and the reference samples were selected after the outlier samples for each amino acid concentration were excluded. The lower limit of the reference intervals for the plasma amino acid concentrations was set at the 2.5th percentile and the upper limit at the 97.5th percentile.

By use of the nested analysis of variance, we analysed a large dataset of plasma samples and the effects of background factors (sex, age and body mass index [BMI]) on the plasma amino acid concentrations. Most amino acid concentrations were related to sex, especially those of branched-chained amino acid. The citrulline, glutamine, ornithine and lysine concentrations were related to age. The glutamate concentration was related to body mass index.

The concentrations of most amino acids are more strongly related to sex than to age or body mass index. Our results indicate that the reference intervals for plasma amino acid concentrations should be stratified by sex when the background factors of age and body mass index are considered.

The menstrual cycle-related changes in clinical laboratory values were analysed by use of data obtained in the Asian multicentre study aimed at derivation of common reference intervals for 85 major clinical laboratory tests.

Among 1876 healthy female volunteers, 893 had regular menstruation. They were classified into five groups according to dates between sample collection and the start of the last menstrual cycle: early follicular phase (1–6 days), late follicular phase (7–12 days), ovulatory phase (13–16 days), early luteal phase (17–22 days), and late luteal phase (23–31 days). Multiple linear regression analysis was performed to evaluate the menstrual cycle-related changes in test results. The magnitude was expressed as a standard deviation ratio of between-phase standard deviation to between-individual standard deviation based on nested ANOVA.

Aside from obvious changes for four sex hormones (oestradiol, progesterone, follicle-stimulating hormone, and luteinizing hormone), we observed statistically significant menstrual cycle-related changes in the following tests (standard deviation ratio >0.15): Na, Cl, creatine kinase, C-reactive protein, serum amyloid A, carbohydrate antigen 125, and parathyroid hormone were higher during the early follicular phase, while insulin, total cholesterol, and white blood cell were higher during the luteal phase. Significant associations of those test items with the four sex hormones were revealed.

The menstrual cycle-related changes in laboratory test results were revealed in some commonly tested items other than sex hormones. The findings are of interest in understanding female physiology in relation to hormonal changes, but the magnitude of changes is rather small and not very relevant in interpreting test results.

Age-specific trends of serum testosterone and sex hormone-binding globulin across the full lifespan have not been reported.

We deduced age-specific trends in serum testosterone and sex hormone-binding globulin in males and females between ages 10 and 90 from a large sample of consecutive results from a single large pathology laboratory. Coded results of 110,712 consecutive blood samples requesting serum testosterone over seven years (2007–2013) comprising blood testosterone, sex hormone-binding globulin and calculated free testosterone together with gender and age were analysed create smoothed age-specific centiles (2.5%, 5%, 25%, 50%, 75%, 95%, 97.5%) for males and females.

These identified the pubertal increases in serum testosterone in males peaking at 20 years of age and remaining stable thereafter until the eighth decade. In females, circulating testosterone peaked in late adolescence and declined gradually over the next two decades but remained stable across menopause and beyond. After early childhood, serum sex hormone-binding globulin declines to a nadir in males at the age of 20 years and remains stable till the sixth decade with a gradual, progressive rise thereafter. In females, the sex hormone-binding globulin nadir is reached earlier with levels rising gradually and progressively with age thereafter and accelerating after the age of 70 years. Females also exhibit a second sex hormone-binding globulin peak during reproductive ages reflected only in upper centiles due to effects of pregnancy and oral contraceptive use in a significant minority of females.

This large sample of clinical data provides a comprehensive profile of androgen status across the lifespan from early adolescence to late old age.

Laboratories are recommended to determine their own local reference intervals (RIs) to embrace the variations in local populations. We have assessed local RIs for thyroid function tests using two different approaches to selection of reference populations and also searched the literature for studies using the Advia Centaur methods.

Two independent populations were made of redundant serum samples from primary care in which exclusion criteria were used to reduce the inclusion of patients with thyroid disease. A further population of healthy subjects were recruited. All groups were restricted to 18–65 years and thyroid peroxidase antibodies (TPOabs) positive subjects were excluded. All samples were analysed using Advia Centaur reagents. A literature search was made for RI studies on non-pregnant adults using Advia Centaur.

Redundant data sets consisted of 219 and 222 subjects and a healthy population of 280. Comparison of variance of all three groups showed differences for free T4 (fT4) and total T3 (TT3) (analysis of variance P < 0.0001) but thyroid-stimulating hormone (TSH) was similar across all three groups (P = 0.7656). RI for TSH, fT4 and TT3 all fell within the 95% confidence interval for each other for all three analytes. Published RIs give wide variation although their mean is similar to the prospective data reported here.

Our data suggest that a consensus set of RIs for Advia Centaur can be adopted from the prospective studies and literature search in this paper and we would suggest the following RIs: TSH 0.5–4.4 mIU/L; fT4 10–20 pmol/L; and TT3 1.1–2.4 nmol/L.

Measurement of aldosterone and/or renin is essential to aid the differential diagnosis of secondary hypertension, guide strategy for therapeutic management of hypertension and assess adequacy of mineralocorticoid replacement.

The objective was to establish normative data for aldosterone and renin using the Immunodiagnostic Systems specialty immunoassay system platform in a Caucasian population.

Following informed consent, 365 subjects were recruited to this study. Subjects were ambulatory and attended clinic for blood pressure measurement and phlebotomy between the hours of 7:00 and 11:00. Blood pressure was measured according to the 2013 European Society of Hypertension/Cardiology guidelines. The inclusion criteria: age ≥18 years, BMI <30 kg/m², non-pregnant, blood pressure <140/90, normal electrolytes and kidney function and not taking prescribed/over the counter medications. Ninety-four subjects were excluded based on these criteria. A total of 271 volunteers (females n = 145), aged 18–65 years formed the reference cohort. Blood for aldosterone/renin was collected into ethylenediaminetetraacetic acid specimen tubes. Samples were kept at room temperature and transported within 30 min of blood draw to the laboratory for immediate processing (centrifugation, separation and freezing of plasma). Plasma was stored at −20℃ prior to analysis on the Immunodiagnostic Systems specialty immunoassay system instrument.

The established reference intervals in an Irish Caucasian population for renin: females: 6.1–62.7 mIU/L, males: 9.0–103 mIU/L, for aldosterone: females: <138–1179 pmol/L, males: <138–670 pmol/L, respectively.

This study demonstrates that reference intervals for aldosterone and renin should be gender specific. These automated immunoassays offer rapid stratification of patients with refractory hypertension and will better facilitate the optimization of therapeutic management.

The demand for measurement of serum immunoglobulin free kappa (κ) and lambda (λ) light chains has increased. The κ:λ ratio is used to assist in diagnosis/monitoring of plasma cell disorders. The binding site reference range for serum-free light chain κ:λ ratios of 0.26–1.65 was derived from healthy volunteers. Subsequently, a reference range of 0.37–3.1 for patients with chronic kidney disease has been proposed. Elevated free light chain concentrations and borderline raised free light chain ratios also may be found in polyclonal gammopathies and with other non-renal illnesses. This assessment was conducted to validate the established free light chain reference ranges in individuals from primary care.

A total of 130 samples were identified from routine blood samples collected in primary care for routine biochemistry testing and estimated glomerular filtration rate calculation.

The median and range of κ:λ ratios found in each estimated glomerular filtration rate group used for chronic kidney disease classification were higher than previously described. This was the case for individuals with normal or essentially normal renal function with estimated glomerular filtration rates>90, (0.58–1.76) and estimated glomerular filtration rate of 60–90 mL/min/1.73 m², (0.71–1.93). Individuals with estimated glomerular filtration rate 15–30, (0.72–4.50) and estimated glomerular filtration rate <15 ml/min/1.73 m² (0.71–4.95) also had higher values when compared to the current renal reference range of 0.37–3.10.

Elevation of free light chain-κ:λ ratios may occur in the absence of a reduced renal function shown by a normal estimated glomerular filtration rate and in the presence of reduced renal function by estimated glomerular filtration rate when comparing results with the established reference ranges. Explanations include choice of analytical systems or the presence of other concurrent non-plasma cell illness.

Previous studies showed high frequency of duplicate errors of lactate dehydrogenase (LDH) measurement in primary lithium-heparin blood tubes. We hence evaluated imprecision of LDH testing and frequency of replicate errors in primary serum samples centrifuged at two different speeds.

Serum samples were collected from 15 healthy subjects and centrifuged at either 1300 g or 2000 g. Serum LDH was then measured on Beckman Coulter AU5800 using the International Federation of Clinical Chemistry-recommended procedure. Complete blood cell count of top layer of serum supernatant was also performed using Advia 2120. Imprecision was calculated as coefficient of variation of 10 replicates of each serum tube, whereas the frequency of replicate errors was compared to the desirable specifications for imprecision.

Mean LDH values were slightly but significantly higher in serum samples centrifuged at 2000 g rather than 1300 g, whereas blood cell counts were similar. The mean imprecision of LDH was more than double in samples centrifuged at 2000 g than in those centrifuged at 1300 g (8% versus 3%). The percentage of replicate measurements exceeding the desirable specifications was more than threefold higher in samples centrifuged at 2000 g than in those centrifuged at 1300 g (30% versus 9%; P < .001).

The lower frequency of replicated errors in LDH measurement observed using serum samples centrifuged according to manufacturer’s instruction suggests that assay precision in serum is better if samples are centrifuged at 1300 g rather than 2000 g when the International Federation of Clinical Chemistry-recommended procedure is used.