J Clin Pathol 1993;46:537-539 537 Correlations between holo- II, holo-haptocorrin, and total B12 in serum samples

from healthy subjects and patients J Clin Pathol: first published as 10.1136/jcp.46.6.537 on 1 June 1993. Downloaded from

S N Wickramasinghe, S Fida

Abstract to cells; this function is performed by TCII.L Aims-To study the correlations between Despite this, most of the B1, in serum is total (B12), holo-haptocorrin, bound to haptocorrin-that is, it is found as and holo-transcobalamin II (holo-TCII) holo-haptocorrin-and in normal subjects concentrations in human sera; the only 6-20% is bound to TCII-that is, it is association between reduced holo-TCII found as holo-TCII.23 Herbert et al have sug- concentrations and macrocytosis attrib- gested that B12 deficiency develops in three utable to B1, deficiency. overlapping stages4: (1) early negative B1, bal- Methods-Serum samples from 38 ance in which holo-TCII concentrations are healthy volunteers, 113 patients with nor- reduced, holo-haptocorrin and total serum mal total serum B12 concentrations and B12 concentrations are normal, and there are 93 patients with low total serum B12 were no biochemical, haematological, or neuro- studied. Holo-TCII was removed from logical consequences of B1, deficiency; (2) B12 whole serum by adsorption with amor- depletion in which holo-TCII and holo- phous precipitated silica, and both whole haptocorrin concentrations are reduced but serum and adsorbed serum were assayed there are no biochemical, haematological, or for B12 using the Becton Dickinson vita- neurological consequences of B1, deficiency; min B12 ["Co] radioassay kit. and (3) B1, deficiency in which, in addition to Results-In all three groups of subjects reduced holo-TCII and holo-haptocorrin studied there were strong correlations concentrations, there are increasing bio- between the logarithms of the total chemical, haematological, or neurological serum B12 and the holo-haptocorrin con- abnormalities attributable to B12 deficiency. centrations with regression coefficients These authors have further proposed that a between 0-884 and 0-967. By contrast, the proper evaluation of the B12 concentration of correlations between the logarithms of an individual must include measurements of the total serum B12 and holo-TCII con- both total serum as well as holo-TCII

B12 http://jcp.bmj.com/ centrations were weaker, especially in concentrations.56 In this study we investi- the patients with normal or low total gated the latter contention by studying the serum B12, for whom the regression coef- correlations between total serum B12, holo- ficients were 0-491 and 0-391, respec- haptocorrin, and holo-TCII concentrations in tively. Analysis of the clinical records of sera from 38 healthy volunteers and 206 a proportion of the patients studied indi- patients, 93 of whom had low total serum B12 cated that there were more many concentrations. on October 1, 2021 by guest. Protected copyright. patients with low holo-TCII concentra- tions than with haematological distur- bances related to B12 deficiency. Methods Conclusions-The total serum B12 con- Sera from 38 healthy adult meat eaters of centration is a relatively poor indicator both sexes, 113 adult patients with normal of holo-TCII concentrations and, there- total serum B12 concentrations, and 93 adult fore, of the ability of serum to deliver B12 patients with low total serum B12 concentra- to tissues. Additional information tions were studied. The sera had been sepa- regarding B12 values can therefore be rated from clotted venous blood within 4 gleaned from measuring holo-TCII con- hours of venesection and stored at -20°C for centrations in the serum. Low holo-TCII up to one month. Total serum B12 concentra- concentrations, however, are an early tions were remeasured in all sera using the Department of sign of negative B12 balance and are Becton Dickinson vitamin B12 [57Co] radio- Haematology, St