Spot urine sampling

Ohira S, Kirk AB, Dyke JV, DasguptaPK (2008) Creatinine adjustment of spot urine samples and 24 h excretion of iodine, selenium, perchlorate, and thiocyanate. Environ Sci Technol 42 9419-9423... 

The urine creatinine concentration should be used to normalize the quantity of any analyte of interest, as this will correct for incomplete urine collection or urine dilution that may have resulted from drinking water spillage within the metabolism cages (Haas et al. 1997). The quantity of creatinine in a spot urine sample serves as an accurate index of the 24 hour urine output in most species. 

Either 24 hour urine collection or timed urine samples collected at the same time each day is recommended, with the activity expressed per unit of time (Price 1982, Plummer et al. 1986). If the assessment is to be repeated with time, the samples should be collected over the same time period on each day because there is pronounced diurnal variation in excretion rate of some enzymes (Maruhn et al. 1977, Price 1982, Gossett et al. 1987). For spot urine samples or those where accurate timed collection is not possible, normalization of activity per unit of creatinine can be done and this has been shown to be reasonably well correlated to 24 hour enzyme activity (Vanderlinde 1981, Grauer et al. 1995). Diet and age-matched controls must be included if enzyme activity is to be normalized to creatinine, to control for the effects of these variables on creatinine excretion (Plummer et al. 1986, Casadevall et al. 1995). 

It should be noted that for urinary excretion studies the preferred design is to collect 24 h urine. In some special designs it can be argued that the use of spot urine samples and correction for urinary creatinine concentration may be a valid measure. A prerequisite for the spot urine - creatinine correction design is a solid argumentation that creatinine excretion is unchanged by the experimental condition or that it is not different between groups. A theoretical example is comparison of lean men versus fat females. Their cell number is comparable but muscle mass very different. Creatinine excretion is mainly... 

Carrier M,Trevisan A, Bartolucci GB. Adjustment to concentration-dilution of spot urine samples correlation between specific gravity and creatinine. Int Arch Occup Environ Health 2001 74 63-67. 

For wounds, any detectable plutonium in the wound or in spot urine samples should warrant considering administration of DTPA. If the activity in the wound is > 5 nCi, excision of tissue should also be considered. 

In the past, measurement of the urinary protein excretion rate was accomplished using a 24-hour urine collection in patients at risk for CKD. Use of an untimed "spot" urine sample with either an albumin-specific dipstick or measurement of albumin creatinine ratio is now recommended by some because it is more convenient than the extended-interval urine collection. 

Widner et al. (1998) used ICP-OES to determine silicon in spot urine samples at the three most sensitive emission vavelengths for silicon that is, 212.412, 251.611 and 288.158 nm. The standard-addition procedure vas applied to meet the requirements of matrix compensation in a frequently changing environment. Addition of EDTA to the urine sample vas recommended to chelate cations, preferentially Ca ", in order to prevent precipitation of poorly soluble salts. 

A longitudinal depiction of the iodine content of 12 consecutive monthly spot urine samples collected from... 

Figure 44.3 Iodine content of 12 consecutive monthly spot urine samples in each of the 15 healthy free-living men in an area with mild-to-moderate iodine deficiency. From Andersen et a ., (2001,2003), reproduced with permission.

These men had mild-to-moderate iodine deficiency, with median urinary iodine content of 50.0 jg/l. Inspection of Rgure 44.3 reveals substantial and random variations in the iodine content of spot urine samples in each of the 15 subjects. No systematic difference between individuals is apparent. 

An additional understanding of individual and group variations is gained if the individual coefficients of variation (CVs) for urinary iodine from Figure 44.1 are added to the individual mean values of urinary iodine content from Figure 44.2, spread out side-by-side. This produces Figure 44.4, in which the iodine contents of the 12 monthly spot urine samples are... 

The overall CV of 57% was in keeping with the CVs of 47% and 52% for men and women, respectively, in a study where spot urine samples were collected at random over a 2-year period in an area with a higher average iodine excretion of 118 p,g/l (Als et al., 2000). 

The variation in estimated 24 h urinary iodine excretion is clearly lower than the variation in iodine concentration in spot urine samples. This improves the accuracy of calculations based on variation in iodine excretion (Andersen et al., 2007a). 

The variation in urinary iodine excretion affects the reliability of estimates of population iodine nutrition. Low urinary iodine is seen in iodine-replete individuals due to random variation (Andersen et al., 2001). However, a high number of samples increases the reliability of the estimates of iodine excretion in a population, but what is the reh-ability of a study including a certain number of spot urine samples from a population ... 

Seek out the column for population in Table 44.4 and find the number of samples. If you have 12000 spot urine samples from a population, the iodine excretion level of... 

Table 44.4 Number of spot urine samples needed to be 95% oonfident of being within a speoified range for crude urinary iodine con-oentration and for estimated 24 hour urinary iodine exoretion oaloulated from the variation in iodine excretion among heaithy men undertaking daily lives (Andersen et al., 2007b)...

When planning a study of iodine nutrition, the number of urine samples needed to describe the iodine excretion level in a population can be read from Table 44.4 (Andersen et al., 2007a). If a precision range of 10% is aimed for, still with 95% confidence, about 125 spot urine samples are needed. Using the estimated 24 h urine iodine excretion reduced the number of samples needed by 20%, i.e., to 100 samples. A precision range of 5% required around 500 spot urine samples, while estimating 24h urinary iodine excretion reduced the required number of spot urine samples to around 400, as can be read from Table 44.4 (Andersen et al., 2007a). 

Again, if the average iodine excretion is 100 tg in 500 samples from a population, the true iodine excretion of that population is likely to be between 95 and 105 p.g with 95% confidence. Given 125 spot urine samples, this will be between 90 and 1 lOpg, equal to widening the precision range to 10%. This is parallel to the validity of subgroup analysis. 

Five hundred spot urine samples describe the iodine excretion level within 5%. 

The median urinary iodine (MUI) concentration provided a measure of the current nutritional status of iodine. MUI was performed in spot urine samples obtained from all mothers and their neonates 5 days after delivery, by using the Sandell—Kolthoff reactions. Decreased MUI excretion of both neonates with hypothyroidism and their mothers was classified as mild-to-moderate iodine deficiency according to the WHO criteria. The mean total thyroid volume (TTvol) of the neonates and their mothers was increased on ultrasonography, whereas no palpable thyroid tissue was detected on physical examination (Table 65.3). 

A Danish study of iodine intake in elderly men and women was made in 1988 after a number of studies had suggested that the iodine intake in Denmark has been stable and relatively low for the last 30 years (Pedersen et ai, 1995). AH subjects were born in 1920 and were thus 68-years old at the time of the study. Iodine was measured in a spot urine sample collected in the morning. Careful investigation of the intake of supplementary iodine was taken into account, which none of the previous studies had done. The median urine excretion was 42p,g/l, which indicates moderate iodine deficiency (see Table 116.1). Analyses among users and nonusers of daily iodine supplements indicated that the basic level of iodine intake was overestimated if individual iodine supplementation was not taken into account. About half of the population took no supplements. 

For the pre-intervention surveys, spot morning urine samples were collected from the first void on waking in the morning. The date and time were recorded. Samples were stored in the dark at 4°C for a maximum of 4 weeks before assay. For the post-intervention surveys casual spot urine samples were collected. An aliquot was drawn from each sample, frozen and transported to the laboratory. 

Chizzotti, ML. Valadares Filho, S.C. Valadares, R.F.D. Chizzotti, F.H.M. Tedeschi, L.O. Determination of creatinine excretion and evaluation of spot urine sampling in Holstein cattle. Livestock Sci. 2008, 113, 218-225. 

Marco, R., Katorza, E., Gonnen, R. et al. (2008). Normalization of spot urine samples to 24-h collection for assessment of exposure to uranium. Radial. Prot. Dosimetry 130, 213-223. 

Another case-control study, conducted in Jamaica, consisted of 175 newly diagnosed prostate cancer cases and 194 controls. The researchers evaluated the relationship of urinary phytoestrogens with total cancer and tumor grade. ENL was measured from spot urine samples. Higher concentrations of ENL were positively associated with both total prostate cancer (OR 1.85 95% Cl 1.01—3.44 p = 0.027) and high-grade disease (OR 2.46 95% Cl 1.11-5.46 p = 0.023). 

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