EAL

GDM: Prevention of GDM Diagnosis (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The objective of this study was to determine whether low plasma chromium concentrations (<=nmol/L) are associated with altered glucose, insulin, or lipid concentration during pregnancy.

Inclusion Criteria:

Women with abnormal results of a 50-g glucose challenge test in the third trimester of pregnancy
The procedures utilized were in accord with the Helsinki Declaration of 1975, revised in 1983.

Exclusion Criteria:

Exclusion criteria was not delineated.

Description of Study Protocol:

Recruitment -Subjects were all selected from clinical population. Recruitment details were not specified.

Design : Cross Sectional

Blinding used- All chromium samples were collected by one investigator.

Intervention (if applicable): not applicable

Statistical Analysis

Means ± standard deviation were presented.
Values that were not normally distributed were presented as with 95% CIs and were compared by using nonparametric Mann-Whitney rank-sum analysis.
Statistics were performed with the use of SPSS (Version 6; SPSSS Inc, Chicago).
The sample size gave a power of approximately 95% with an alpha of 5% to detect a difference of 0.75 SD in fasting glucose, 2-h glucose, insulin, cholesterol, or triacylglycerol between groups with normal compared with abnormal chromium measurements.

Data Collection Summary:

Timing of Measurements

One time measurement.

Dependent Variables

Oral glucose tolerance test-interpreted by the guidelines of the Australasian Diabetes in Pregnancy Society; a fasting plasma glucose concentration >=5.5 or a 2-h value >=8.0 nmol/L is considered abnormal.
Plasma glucose was measured by the hexokinase method .
Fasting insulin was measured by by radioimmunoassay (Phadaseph AB, Uppsala, Sweden).
Total cholesterol was measured by enzyme colorimetric testing (Boehringer Mannheim Systems, Mannheim, Germany).
Triacylglycerols were measured by enzyme colorimetric testing (Boehringer Mannheim Systems).
Chromium was measured by graphic furnace atomic absorption spectrometry with a Varian SpectrAA800 Zeeman effect instrument from Varian Australia P/L , Melbourne. The laboratory performing the determination participated in the qualaity- assurance program for chromium in serum conducted by Quality Control Technologies (Charlestown, Australia). No alternative techniques for measurement of serum chromium were available.
With the use of the homeostasis model, insulin resistance was calculated with the formula insulin/(22.5e ^__In ^glucose).
ß Cell function was calculated with use of the formula 20 X insulin/ (fasting glucose –3.5).

Independent Variables

Age (y)
Height (cm)
Prepregnancy weight (kg)
Prepregnancy BMI (kg/m²)
Parity
Pregnancy interval (mo)
Race (white/Asian/Arabic)
Time of gestation (wk)

Control Variables

Description of Actual Data Sample:

Initial N: 79

Attrition (final N): 79

Age: The mean age of the participants 32± 4 y.

Ethnicity: white/Asian/Arabic

Other relevant demographics:

Anthropometrics

Location: Department of Endocrinology and Pacific Laboratory Medicine Services, Royal North Shore Hospital, St Leonards, Australia.

Summary of Results:

There were no significant differences in patient characteristics when women with chromium concentrations <=3 nmol/L were compared with concentrations >3 nmol/L (Table 1 and Table 2).

Table I: Patient characteristics for the group as a whole and subdivided by serum chromium concentration

	All patients-	Patients with chromium<=3 nmol/L	Patients with chromium>3 nmol/L
n	79	63	16
Age (y)	32±5¹	32±4	32±5
Height (cm)	163±6	164±7	162±7
Prepregnancy weight(kg)	58(44,98)²	60(34,130)	56(45,79)
Prepregnancy BMI(kg/m²)	21.9(16.2,37.1)	22.0(14.7,46.6)	21.5(18.1,33.0)
Parity	0.7(0-3)³	0.6(0-3)	0.8(0-3)
Pregnancy interval(mo.)	14	15	14
Race(white/Asian/Arabic)	50/20/8	41/17/5	10/3/3
Time of gestation (wk)	29(21,35)	29(25,34)	29(28,35)

1. Mean+ 1 SD; 2. Median (95% CI); 3. Median; range in parentheses.

Table 2 Variables in the group as a whole and subdivided by serum chromium concentrations

	All patients-	Patients with chromium<=3nmol/L	Patients with chromium>3 nmol/L
n	79	63	16
50-g challenge(nmol/L)	8.8±1.0¹	8.8±1.1	8.6±0.8
Fasting glucose(nmol/L)	4.7±0.6	4.7±0.6	4.8±0.4
2-h glucose(mmol/L)	7.2±1.8	7.4±1.9	6.8±1.2
Insulin (pmol/L)	9.2(2.9,30.3)²	9.2(2.9,34.6)	9.7(2.0,16.0)
Total cholesterol(mmol/L)	6.7±1.1	6.7±1.2	6.7±0.9
Triacylglycerol(mmol/L)	2.2±0.7	2.3±0.7	2.0±0.6
Chromium (nmol/L)	2(0,10)	1(0,3)	5(4,11)
Gestational diabetes	25(31.6)	22(34.9)	3(18.8)
Insulin resistance	1.9(0.5,7.4)	1.9(0.6,7.6)	1.9(0.4,6.0)
ßCell function	166(59,1068)	166(74,3461)	165(31,591)

1. Mean + 1 SD. There were no significant differences; 2. Median (95% CI).

There were no significant associations when chromium was tested as a continous variable (Table 3).

Table 3 Correlation coefficients (r) of the variables for 79 patients

	BMI	Fasting blood glucose	2-h blood glucose	Insulin	ßCell function	Insulin resistance	Total chol.>>>	Triacylglycerols
Chromium	-0.051	-0.005	-0.082	-0.176	-0.107	-0.159	-0.007	-0.152
BMI	-----------	0.361¹	0.140	0.463²	0.285³	0.514²	-0.012	0.230
Fasting blood glucose	-	-	0.449²	0.456²	-0.304¹	0.639²	-0.266³	0.305¹
2-h blood glucose	-	-	_	0.091	-0.141	0.202	-0.17	0.194
Insulin	_	_	_	_	0.1	0.970¹	-0.202	0.305¹
ßCell function	_	_	_	_	_	0.021	0.05	-0.017
Insulin resistance	_	_	_	_	_	_	-0.277³	0.298¹
Total cholesterol	_	_	_	_	_	_	_	0.232³

1. P<0.01; 2 .P<0.001; 3. P<0.05

A literature search did not locate any studies of serum chromium measurement in pregnancy. Studies of chromiun supplementation are summarized in Table 4.

Table 4 Summary studies of chromium supplementation¹

Diabetes Mellitus Status	Reference	No. of subjects	Form of supplemntation and dosage	Duration	Significant effects
			µ/d
No	Hopkins et al(19)	12	CrCl_{3 ,} 250	1 d	Elev GT
No	Levine et al(20)	10	CrCl_3,150	12-16 wk	Elev GT
No	Carter et al (21)	9	CrCl_{3 ,} 250	1-4 d	none
No	Gurson et al(22)	15	CrCl_{3 ,} 50	1-6 wk	Elev GT
No	Riales and Albrink(23)	14	CrCl_{3 ,} 200	12 wk	Elev HDL chol
No	Anderson et al (10)	76	CrCl_{3 ,} 200	12 wk	variable
No	Offenbacher and Pi-Sunyer(6)	8	CrCl_{3 ,} 300	10 wk	none
No	Potter et al(24)	5	CrCl_{3 ,} 200	5 wk	Elev BCF
No	Martinez et al(25)	85	CrCl_{3 ,} 200	10wk	Elev GT
No	Bourn et al (26)	47	CrCl_{3 ,} 200	10wk	Elev HDL
No	Urberg and Zemmel(27)	16	CrCl_{3 ,} 200,niacin	4 wk	Elev GT
No	Urberg et al(28)	2	CrCl_{3 ,} 200,niacin	52 wk	decreased chol
No	Wang et al(29)	10	CrCl_{3 ,} 50	12 wk	decreased chol & LDL
No	Press et al(30)	28	Cr pic, 200	6 wk	decreased chol & LDL
No	Lefavi et al(31)	34	Cr nic 2-800	8 wk	decreased chol
No	Anderson et al (32)	17	CrCl_{3 ,} 200	8 wk	Elev GT
No	Roeback et al(33)	63	BA Cr,600	8 wk	Elev HDL
Yes	Roeback et al(33)	63	BA CR ,600	8 wk	Elev HDL
Yes	Glinsman and Mertz(34)	6	CRCL_3,180-1000	<20 wk	Elev GT in 3 of 6
No	Glinsman and Mertz(34)	10	CRCL_3,180-1000	1-50 wk	None
No	Offenbacher and Pi-Sunyer(35)	8	Yeast Cr,11	8 wk	Elev GT, decreased chol
Yes	Offenbacher and Pi-Sunyer(35)	8	Yeast Cr,11	8 wk	Elev GT, decreased ins
No	Abraham et al (36)	51	CRCL_3,250	28-64 wk	Elev HDL,decreased TG
Yes	Abraham et al (36)	25	CRCL_3,250	28-64 wk	Elev HDL,decreased TG
No	Uusitupa et al (37)	26	Yeast Cr, 160	24 wk	None
Yes	Uusitupa et al (38)	10	CRCl₃, 200	6 wk	decreased ins (60 min)
No	Wilson and Gondy(39)	26	Cr pic,220	14 wk	decreased ins
No	Thomas and Gropper(40)	14	Cr nic,200	14 wk	None
yes	Sherman et al(41)	7	CrCl₃,50	16 wk	None
yes	Nath et al(42)	12	Reduced Cr,500	8 wk	Elev GT, decreased ins,decreased chol
yes	Rabinowitz et al (43)	43	CrCl₃, 150	16 wk	None
yes	Mossop(44)	26	CrCl₃, 600	16-32 wk	decreased fasting glucose
yes	Elias et al(45)	6	Yeast Cr , 21	2 wk	decreased fasting glucose
yes	Evans(46)	11	Cr pic,200	6 wk	decreased Hb A_1c,decreased LDL
Yes	Lee and Reasner(47)	28	Cr pic,200	8 wk	decreased TG
Yes	Ravina(48)	162	Cr pic,200	10 d	decreased glucose, decreased ins
Yes	Thomas and Gropper(49)	5	Cr nic,200	8 wk	None
Yes	Anderson et al(50)	185	Cr pic,200-1000	16 wk	decreased Hb A_1c, decreased chol
Yes	Fox and sabovic (51)	1	Cr pic,600	1 wk	decreased Hb A_1c
Yes	Jeejeebhoy et al (1)	1	CrCL_3,200	1 wk	Reversal of diabetes
Yes	Freund et al (2)	1	CrCL_3,100	1 wk	Reversal of diabetes
yes	Brown et al (3)	1	CrCL_3,200	1 wk	Reversal of diabetes
Gestational	Javanovic-Peterson et al (52)	8	Cr pic,1-600	3-10 wk	decreased glucose

1. GT,glucose tolerance; chol,cholesterol; BCF, ß cell function; pic,picolinate; nic,nicotinate; BA,biologically active; ins,insulin;Hb A _{1c ,}glycated hemoglobin; Tg, triacylglycerol.

Other Findings

Author Conclusion:

Plasma chromium during pregnancy does not correlate with glucose intolerance, insulin resistance, or serum lipids.
The sample size gave a power of approximately 95% with an alpha of 5% to detect a difference of 0.75 SD in fasting glucose,2-h glucose, insulin, cholesterol, or triacylglycerol between groups with normal compared with abnormal chromium measurements.

Limitation:

Plasma chromium concentrations may not adequately accurately reflect tissue stores of chromium.

Funding Source:

University/Hospital:

Royal Northshore Hospital

Reviewer Comments:

A cross sectional study measures the prevalence of health outcomes or determinants of health, or both, in a population at a point in time or over a short period. However, associations must be interpreted with caution. Bias may arise because of selection into or out of the study population. A cross sectional design may also make it difficult to establish what is cause and what is effect.

The limitation and critique of the study, as stated by the authors appear to be very appropriate.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	???
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	???

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	Yes
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		N/A
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		???
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	???
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	Yes
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes