Vitamin B1
The main circulating form of vitamin B1 is thiamin diphosphate (TDP) which is found almost completely in red blood cells. Alternative forms of vitamin B1 are thiamin, thiamin monophosphate and thiamin triphosphate. All forms of vitamin B1 can be interconverted in vivo. TDP is an important cofactor for enzymes involved in carbohydrate metabolism. It is a cofactor for several enzymes, such as pyruvate dehydrogenase, oxoglutarate dehydrogenase and transketolase (transketolase activity is sometimes measured as an indicator of vitamin B1 deficiency). Thiamin triphosphate (TTP) is thought to be important in nerve conduction.
Deficiency and Toxicity
Body stores of vitamin B1 are low (~30mg) and so deficiency can develop fairly quickly. 50% of vitamin B1 stores are in skeletal muscle and the rest in heart, kidneys, liver and nerve tissue.
Deficiency is most commonly associated with low intake (eg. in alcoholics, elderly), severe protracted vomiting, increased requirements (exertion, pregnancy, fever, breast feeding and rapid adolescent growth) or increased loss (haemodialysis). Deficiency can result in peripheral neuropathy, encephalopathy, muscle pain and tenderness, and congestive cardiac failure. The encephalopathy known as Wernicke Korsakoff syndrome, consists of abnormal eye movement and gait, confusion and memory loss.
Toxicity resulting from high doses of vitamin B1 has not been described, except for occasional instances of non-immune anaphylaxis.
Assessment of status
The TDP concentration in erythrocytes has been shown to be a good indicator of body stores because it depletes at a rate similar to those of other major organs.72
Since almost all (>90%) vitamin B1 is present in red blood cells, assessment of status is by measuring TDP concentration in either in whole blood or packed red cells.
Measurement of TDP in erythrocytes has been shown to be a more sensitive indicator of vitamin B1 status than the transketolase activation assay73,74,75 which is an indirect measurement of status.
Work done in this unit shows that the systemic inflammatory response does not affect red cell vitamin B1 concentration in patients 48 hours after undergoing elective surgery for knee arthroplasty (see Table).76 The systemic inflammatory response, therefore, does not affect vitamin B1 status when assessed by red cell TDP measurement.
Recommended Daily Allowance
Adults: 1.2 mg/day
Effect of Systemic Inflammatory Response on Plasma TDP Concentrations
Table: Baseline, peak/ trough and day 7 concentrations of CRP and thiamin diphosphate (TDP) following elective surgery for knee arthroplasty (n = 20).76
| Baseline values (0 h) | Peak/trough (48 h) |
Final values (168 h) |
Friedman (0–168 h) |
|
|
CRP (mg/L) |
<6 (<6–<6) | 170 (70–242) | 31 (<6–168) | <0.001 |
|
Red cell TDP (ng/g Hb) |
411 (351–549) | 462 (305–600) | 413 (353–552) | 0.015 |
Sample Requirements and Reference Ranges for Vitamin B1
| Sample Type | Whole blood (fasting sample preferred*) |
|---|---|
| Container | Lithium heparin (non-gel) or EDTA. |
| Precautions |
Vitamin B1 stable if delivered to lab within 72 hours. If delivery to Glasgow is outwith 72 hours, store whole blood frozen until sending and then send by first class post (not on ice or dry ice). Lithium heparin gel tubes are unsuitable. In parenterally fed patients we recommend a fasting sample or sample collected 8 hours after last feed. |
| Minimum volume** | 350 µL |
| Reference ranges |
275 to 675 ng/g Hb73 150 to 275 ng/g Hb (subclinical deficiency) <150 ng/g Hb (clinically deficient) |
| Mean turnaround time | 4.3 days (see this page for STEMDRL TAT targets) |
| Method | HPLC with fluorimetric detection (In-house method).73 |
| Traceability | EQA. Please contact laboratory for current EQA performance. |
| Intermediate Precision (CV) | See this page for latest data |
| Measurement Uncertainty, U | See this page for latest data |
| Analytical Goals (CV) |
See this page for latest data |
| EQA Scheme | INSTAND scheme Düsseldorf, Germany (four times per year). |
| Included in UKAS scope? | Yes |
* Ideally a fasting sample should be collected, especially if the patient is receiving oral or parenteral vitamin B1 supplementation. If this is not possible, sample should be taken at least 8 hours post treatment for patients receiving oral supplementation or TPN.
** Absolute minimum volume; this volume is insufficient to carry out repeat analysis if analysis fails.