Intraindividual variation

Brock A. 1991. Inter and intraindividual variations in plasma cholinesterase activity and substance concentration in employees of an organophosphorus insecticide factory. Br J Ind Med 48 562-567. 

Kalow, W., Tang, B. K. Endrenyi, L. (1998). Hypothesis comparisons of inter- and intraindividual variations can substitute for twin studies in drug research. Pharmacogenetics, 8, 283-9. 

Grem JL, Yee LK, Venzon DJ et al. Inter-and intraindividual variation in dihydropyrimidine dehydrogenase activity in pe-... 

In view of the intraindividual variation in olfactory sensitivity, which may be quite considerable, a panel of six subjects would be the absolute minimum. 

R. H. Larsen, F. Nielsen, J. A. Sorensen, and J. B. Nielsen. Dermal penetration of fentanyl Inter- and intraindividual variations. Pharmacol. Toxicol. 93 244-248 (2003). 

As the discount factor at delay t = 0 should be equal to 1, we can— without loss of generality—set p = 1. Ainslie has no theory of interindividual or intraindividual variations in the parameter a and seems to conceive a as fixed. Obviously, a depends on the units of measurement for time. Hence, as long as we are not making interpersonal comparisons, we may choose the time unit so that a reward delayed one time unit is valued as half of its instantaneous value. This implies that a = 1, and we obtain... 

The peak plasma concentration is reached 2 h after oral administration. The degree of binding of phenylbutazone to plasma proteins is 98%. The long elimination half-life of phenylbutazone (mean -70 h) exhibits large interindividual and intraindividual variation. It is metabolized in the liver by oxidation and glucuronidation and excreted in the urine and to a lower degree (-25%) in the faeces (Aarbakke, 1978). Oxyphenbutazone is an active metabolite of phenylbutazone. The metabolic pathway of phenylbutazone is shown in Scheme 72. 

The potential sources of variability for gastric residence in the fed mode are the size of the pyloric opening versus the tablet size, the rate of reduction in the size of the tablet by dissolution and antral grinding by the stomach, and inter- and intraindividual variations in the duration of the fed mode, particularly as a function of caloric and fat content. The dominant limitation in the use of food for gastric retention is the minimal total fat content. 

It should also be emphasized that although the precision of the automated particle-enhanced immunometric methods is higher than that of the enzyme-amplified single radial immunodiffusion first used to quantitate serum cystatin C, it is still lower than that for most methods for determination of serum creatinine. Moreover, the data for the intraindividual variation of serum cystatin C strongly indicate that a higher precision of the method would markedly improve the clinical usefulness of serum cystatin C determinations according to the criterion of Cotlove (N6). 

However, torsades de pointes does not occur in every patient who is treated with these drugs. Large intraindividual variations in QT prolongation are common. Other factors that may predispose to this arrhythmia include hypokalemia, hypomagnesmia, hypothyroidism, renal failure, and congestive heart failure (95, 97, 101, 102). 

The metabolism and pharmacokinetics of the carotenoids are not well understood, and their bioavailabUity is associated with much interindividual and intraindividual variation (281). p-Carotene, a-carotene, cryptoxanthin, lycopene, and lutein are the major carotenoids in human serum, and lycopene and p-carotene are the major carotenoids in other human tissues (282). Small amounts of zeax-anthin, phytofluene, and phytoene are also found in various organs. Various carotenoids tend to be present in similar ratios in human plasma and tissues (282, 283). The carotenoids are safe and even long-term intake of 180 mg of p-carotene per day did not lead to hypervitaminosis. When large amounts of carotenoids are stored in the adipose and other lipid-rich tissues, they may cause reversible yellowing of the... 

Insulin formulation Ultra-short-acting Insulin (half-life 0.5-2 hours) Regular Insulin (half-life 2-4 hours) Intermediate-acting Insulin (half-life 16-20 hours) Prolonged-acting insulin (half-life 36 hours and over) Intraindividual variation In absorption up to 50% Interindividual variation from day-to-day up to 25%... 

Clinical trials on the effects of long-acting insulin analogues showed only a small intraindividual variation of absorption from the injection site with an... 

TABLE 3 Intraindividual variations in the metabolism of phenacetin as measured by AUC values... 

Alvares AP, Kappas A, Eiseman JL, Anderson KE, Pantuck CB, Pantuck EJ, Hsiao K-C, Garland WA, Conney AH. 1979. Intraindividual variation in drug disposition. Clin. Pharmacol. Ther. 26 407-19... 

From Statland BE, Bokelund El, Winkel P Factors contributing to intraindividual variation of serum constituents 4. Effects of posture and tourniquet application on variation of serum constituents in healthy subjects. Clin Chem. 1974 20 1513-19,... 

Categories of biological variation include (1) within an individual and (2) between individuals. The change of laboratory data around a hemostatic set point from one occasion to another within one person is called within-subject or intraindividual variation (Table 17-14). The difference... 

It is possible to substitute the coefficient of variation for the standard deviation in the above equation. If the conditions of patient preparation, sample collection, and sample handling are standardized, preanalytical variation is minimized and the total variation is then determined by the combined influence of the analytical and intraindividual variations, thus ... 

Although it would be preferable if the range of values in an mdividual when healthy could be used as the reference for the same individual when he or she is ill, this is largely impractical. The less specific reference interval derived from many individuals must be used as a guide to determine whether a specific result is abnormal. The index of individuality (II) allows a comparison of total within-subject (intraindividual) variation to between-subject (inter-individual) variation. It is calculated as the ratio of the total intraindividual variation to interindividual biological variation as... 

The index of heterogeneity (IH) provides a means of determining whether the individuals within a population have similar withiii-individual variation for a given analyte. It is is defined as the ratio of CV of (SDl + to [2/ n - 1)] where A and I are the analytical and within-subject variations and n is the number of specimens per subject. The higher the index of heterogeneity the greater the intraindividual variation. 

The RCV concept is used to determine the most appropriate mode to report several analytes where several possibilities exist. For example, the amount of an analyte in urine could be reported in terms of concentration, absolute amount per unit of time, or the amount relative to that of creatinine. The mode with the smallest relative change value is the most informative. Data on analytical and intraindividual variation together with RCV can pinpoint the most appropriate type of specimen for certain analyses. Howey et studied random, early morning, and 24-hour urine specimens to determine the most appropriate means to monitor microalbuminuria. The first morning specimen became the preferred specimen because of its smallest within-individual variation, smallest heterogeneity in intraindividual variances, and smallest RCV between consecutive measurements. 

Data on biological variability are used to assist in the selection of the most appropriate test in a given situation. For example, creatinine clearance and urine creatinme have less intraindividual variation than serum creatinine so that creatinine clearance is a better choice than serum creatinine for initial assessment of renal function in an individual but the lower RCV for serum creatinine make this test better for monitoring individuals. However, the need for a urine collection reduces the practicality of using clearance in the initial assessment of renal function. Studies to determine whether the GFR calculated from the serum creatinine concentration might enhance the utility of the serum measurement still have to be performed. 

Statland BE, Winkel P. Effects of preanalytical factors on the intraindividual variation of analytes in the blood of healthy subjects Consideration of preparation of the subject and time of venipuncture. CRC Crit Rev Clin Lab Sci 1977 8 105-44. 

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