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Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons.
Nutrition. 2004 Sep; 20(9):764-8.N

Abstract

OBJECTIVES

We sought to determine the cutoffs of fasting urinary methylmalonic acid (MMA) indicating elevated and mildly elevated serum MMA concentrations in older persons.

METHODS

We studied 113 female Chinese vegetarians older than 55 y with normal renal function. Fasting serum samples were obtained for measurement of vitamin B12, MMA, and folate and tests of renal function. A fasting urine sample was collected for MMA measurement by the stable-isotope dilution method. The correlation between serum and urinary MMA levels was examined. The optimal cutoffs of urinary MMA for predicting elevated and mildly elevated serum MMA were estimated by use of receiver operating characteristic curves.

RESULTS

Fasting urinary and serum MMA levels were linearly correlated. Pearson's correlation coefficient was 0.94. The cutoff of fasting urinary MMA of 2 microM/mM of creatinine had a sensitivity of 79%, a specificity of 85%, and a positive predictive value of 93% for elevated serum MMA (> 0.4 microM/L). A cutoff of 1.5 microM/mM of creatinine had a sensitivity of 86%, a specificity of 85%, and a positive predictive value of 95% for mildly elevated serum MMA (> 0.3 microM/L). Both cutoffs had high positive predictive values for subnormal vitamin B12 concentrations.

CONCLUSION

Overnight fasting urinary MMA concentrations have a strong linear relation to serum MMA in older vegetarians without renal impairment. Urinary MMA is potentially useful as a screening tool for metabolic vitamin B12 deficiency in older persons.

Authors+Show Affiliations

Department of Medicine and Therapeutics, Shatin, Hong Kong, Peoples' Republic of China. tkwok@cuhk.edu.hkNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

15325684

Citation

Kwok, T, et al. "Use of Fasting Urinary Methylmalonic Acid to Screen for Metabolic Vitamin B12 Deficiency in Older Persons." Nutrition (Burbank, Los Angeles County, Calif.), vol. 20, no. 9, 2004, pp. 764-8.
Kwok T, Cheng G, Lai WK, et al. Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons. Nutrition. 2004;20(9):764-8.
Kwok, T., Cheng, G., Lai, W. K., Poon, P., Woo, J., & Pang, C. P. (2004). Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons. Nutrition (Burbank, Los Angeles County, Calif.), 20(9), 764-8.
Kwok T, et al. Use of Fasting Urinary Methylmalonic Acid to Screen for Metabolic Vitamin B12 Deficiency in Older Persons. Nutrition. 2004;20(9):764-8. PubMed PMID: 15325684.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons. AU - Kwok,T, AU - Cheng,G, AU - Lai,W K, AU - Poon,P, AU - Woo,J, AU - Pang,C P, PY - 2004/8/25/pubmed PY - 2005/3/18/medline PY - 2004/8/25/entrez SP - 764 EP - 8 JF - Nutrition (Burbank, Los Angeles County, Calif.) JO - Nutrition VL - 20 IS - 9 N2 - OBJECTIVES: We sought to determine the cutoffs of fasting urinary methylmalonic acid (MMA) indicating elevated and mildly elevated serum MMA concentrations in older persons. METHODS: We studied 113 female Chinese vegetarians older than 55 y with normal renal function. Fasting serum samples were obtained for measurement of vitamin B12, MMA, and folate and tests of renal function. A fasting urine sample was collected for MMA measurement by the stable-isotope dilution method. The correlation between serum and urinary MMA levels was examined. The optimal cutoffs of urinary MMA for predicting elevated and mildly elevated serum MMA were estimated by use of receiver operating characteristic curves. RESULTS: Fasting urinary and serum MMA levels were linearly correlated. Pearson's correlation coefficient was 0.94. The cutoff of fasting urinary MMA of 2 microM/mM of creatinine had a sensitivity of 79%, a specificity of 85%, and a positive predictive value of 93% for elevated serum MMA (> 0.4 microM/L). A cutoff of 1.5 microM/mM of creatinine had a sensitivity of 86%, a specificity of 85%, and a positive predictive value of 95% for mildly elevated serum MMA (> 0.3 microM/L). Both cutoffs had high positive predictive values for subnormal vitamin B12 concentrations. CONCLUSION: Overnight fasting urinary MMA concentrations have a strong linear relation to serum MMA in older vegetarians without renal impairment. Urinary MMA is potentially useful as a screening tool for metabolic vitamin B12 deficiency in older persons. SN - 0899-9007 UR - https://www.unboundmedicine.com/medline/citation/15325684/Use_of_fasting_urinary_methylmalonic_acid_to_screen_for_metabolic_vitamin_B12_deficiency_in_older_persons_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0899900704001595 DB - PRIME DP - Unbound Medicine ER -