Measurement reference intervals

A and E refer to the desorption, dissociation, decomposition or other surface reactions by which the reactant or reactants represented by M are converted into products. If [M] is constant within the temperature interval studied, then the values of A and E measured refer to this process. Alternatively, if the effective magnitude of [M] varies with temperature, the apparent Arrhenius parameters do not specifically refer to the product evolution step. This is demonstrated quantitatively by the following example [36]. When E = 100 kJmole-1 andA [M] = 3.2 X 1030 molecules sec-1, then rate coefficients at 400 and 500 K are 2.4 X 1017 and 1.0 X 1020 molecules sec-1, respectively. If, however, E is again 100 kJ mole-1 and A [M] varies between 3.2 X 1030 molecules sec-1 at 500 K and z X 3.2 X 1030 molecules sec-1 at 400 K, the measured values of A and E vary significantly, as shown in Fig. 7, when z ranges from 10-3 to 103. Thus, the measured value of E is not necessarily identifiable with the rate-limiting step if a concentration of a participant is temperature-dependent. This... 

Oxime derivatization was utilized by Kushnir et al. [44] to improve ESI sensitivity for testosterone measurement. Using a C18 column for separation (3-min run times) and an API 4000 they monitored MRM transitions 304—>124 and 112 for testosterone oxime and 307—>14 and 112 for the d3 internal standard. Within-run and between-run irreproducibility was < 12%. The LOD was 10 pg/ml, allowing accurate measurement of testosterone in women and children. Reference intervals for the steroid in children of different ages and different Tanner stages are given in the publication as well as values for both free and total testosterone. 

Range of measurement 5-55 mmol/1. Reference interval 22-31 mmol/1. 

Range of measurement 5.0-40.0 mmol/1. Reference interval 22-30 mmol/1. Sample Serum or heparin plasma. Interferences ... 

Range of measurement 50-175 mmol/1. Reference interval 98-107 mmol/1. 

Measurement wavelength 670 nm Reference interval Not given. Sany)le material serum... 

E457 Lockitch, G., Halstead, A.C., Albersheim, S., MacCallum, C. and Quigley, G. (1988), Age- and sex-specific pediatric reference intervals for biochemistry analytes as measured with the Ektachem-700 analyzer. Clin. Chem. 34, 1622-1625. 

Range of measurement 2-12 mmol/1 or mval/1. Reference interval ... 

Sample material Serum, EDTA plasma or heparin plasma. Dilution of samples 1 part sample + 8 parts de-ionised water. Range of measurement 40-500 mg/dl or 0.45-5.65 mmol/1. Reference interval 20-180 mg/dl or 0.23-2.05 mmol/1. Interferences ... 

Reference interval In healthy humans the highest plasma cortisol concentration was measured between 5 and 10 a.m. The lowest levels were seen at 8 p.m. and 4 a.m. Serum cortisol concentrations drop late in the afternoon by about 1.5-fold of the morning level. 

The factors for converting from traditional to SI units for many of the constituents of body fluids commonly measured in the clinical laboratory are Hsted in the table of reference intervals in Chapter 56. 

It is often claimed that the analytical quality should be better when determining reference values than when producing routine values. This may be true for accuracy aU measures should be taken to eliminate bias. The question of imprecision is more difficult because it depends partly on the intended use of the reference values. Increases in analytical random variation result in widening of the reference intervals For some special uses of reference values, the narrower reference interval obtained by a more precise analytical method may be appropriate. However, this is usually not true... 

Nephelometry, immunoturbidimetry, electroimmunodiffu-sion, and RID are most often used for measurements of albumin and IgG in cerebrospinal fluid. Apparent absence of IgG may be due to its. degradation by proternases in the specimen. RIA is required for determination of specific pro-teins present in very low concentrations (e.g., IgM). The reference interval for albumin levels in lumbar CSF by RID is 17.7 to 25.1 mg/dL. IgA, IgD, and IgM, measured by RIA, are each normally less than 0.2 mg/dL. Reference intervals for IgG are age related their means increase from 3.5 mg/dL in the 15- to 20-year-old group to 5.8 in adults aged 60 or older. The usual reference interval for CSF IgG in adults is 0.8 to 4.2 mg/dL for total protein, 15 to 45 mg/dL. Total protein levels are considerably higher in neonates, and in healthy elderly adults, concentrations up to 60 mg/dL are considered normal. 

Serum CK activity is influenced by age, sex, race, lean body mass, physical activity, and other less defined genetic differences. The distributions of CK activity are notably skewed toward higher values in reference populations. Men have higher values than women, and blacks have higher values than nonblacks. In Caucasian subjects, the reference interval was found to be 46 to 300 U/L for males and 34 to 180U/L for females when measured at 37 °C. Experience with the IFCC 37 °C reference procedure has shown reference intervals of 46 to 171 U/L for males and 34 to 145 U/L for females. ... 

The reference interval for the activity of ALD in adults is 2.5 to lOU/L, measured at 37 °C. However, there is a definite sex difference with men having higher values. Serum ALD in the neonate is fourfold the adult activity and in children is twice that of the adult. Adult values are attained by the time the child reaches puberty. ... 

Pagani F, Bonora R, Panteghini M. Reference interval for lactate dehydrogenase catalytic activity in serum measured according to the new IFCC recommendation. Clin Chem Lab Med 2003 41 970-1. 

Given the discussion above, reference intervals for plasma creatinine are clearly method dependent. Typically, reference intervals for plasma creatinine, measured by Jaffe methods, are 0.9 to 1,3 mg/dL (80 to 115 p,mol/L) in men and 0.6 to 1.1 mg/dL (53 to 97p.mol/L) in women. Plasma creatinine concentration in patients with untreated end-stage renal disease (ESRD) may exceed 11 mg/dL (lOOOlxmol/L). Reference intervals for plasma creatinine are also listed in Chapter 56. 

Kidney Stones. About one in five patients with clinical gout also has urinary tract uric acid stones. Although plasma and urinary uric acid should he measured in stone formers, many uric acid stone formers do not demonstrate either hyperuricuria or hyperuricemia. However, this may reflect the use of reference intervals derived in a purine-rich, westernized society.The etiology of uric acid stone formation also involves the passage of a persistently acid urine with loss... 

The choice of the type of assay to be used for such measurements depends on the expected concentration of the protein to be measured. For example, in the case of albumin, the assay chosen must be precise at the upper limit of the reference interval (for maximal clinical effectiveness), while also being able to ensure that antigen excess does not occur at high pathological concentrations. In practice, this cannot be achieved in a direct aggregation assay, where the antibody-created particles are aggregated in the presence of... 

Cystatin C has been measured by immunodiffusion or rocket electroimmunoassay, but the methods are too insensitive, and any form of labeled immunometric assay is too cumbersome and time consuming for the response time required. The most practical approaches described are to use a latex particle-enhanced turbidimetric or nephelometric immunoassay. An intraassay precision of less than 3% can be expected at the upper limit of the reference interval ( 1.00mg/L), with less than 4% for the between-day value. Further, cystatin C measurement appears unaffected by the spectral interferences affecting creatinine assays. ... 

Fasting venous blood, drawn with a patient at rest, has a pyruvate concentration of 0.03 to O.lOmmol/L (0.3 to 0.9mg/dL). Arterial blood contains 0.02 to 0.08mmol/L (0.2 to 0,7mg/dL). Values for CSF are 0.06 to 0.19mmol/L (0,5 to 1.7mg/dL), Age-related reference intervals in CSF have been estabfished in children. Urine output of pyruvate is normally Immol/day or less. There are few clinical indications for measurement of blood pyruvate concentrations. 

Values for GHbs are expressed as a percentage of total blood hemoglobin. One of three major GHb species, namely Hb Ai, Hb A,c, or total GHb, is usually measured. In the United States, the vast majority of laboratories now measure Hb Ale. Reference intervals vary, depending on the GHb component measured and whether the labile fraction is included in the assay. A consensus, based on several studies of apparently healthy subjects, suggests the following reference intervals ... 

---