A novel screening tool (Karanth's test) for vitamin B12 deficiency: a pilot study

No practical tests are currently available for screening vitamin B12 deficiency because the available techniques are invasive, expensive, and require a particular level of infrastructure and service that is not available in all places such as rural areas. Thus, we have examined the efficacy of a novel method (Karanth's test) for identifying people with vitamin B12 deficiency as part of a pilot study.

An observer-blind study was conducted on 83 consenting patients from a tertiary teaching hospital whose blood was drawn for estimation of serum vitamin B12 over a 2-month period. All of these patients completed the study. In the Karanth's test, the skin color tone is measured at the interphalangeal joint and the phalanx using the Von Luschan skin tone chart. The test result is obtained from differences in the values obtained. This test was performed on the day blood was drawn to measure the serum vitamin B12 levels in the study patients and on every day until discharge for patients tested to be deficient.

Of the 83 patient subjects, 20 showed deficient vitamin B12 levels in the blood test. The Karanth's test readings were significantly different for patients with normal and deficient levels of vitamin B12 (95 % CI, 0.838-2.153). ROC curve analysis suggested that a difference greater than 1.5 should be considered positive. The sensitivity and specificity of the test were determined to be 80 and 84.1 %, respectively. Patients were grouped further according to the Fitzpatrick scale. There were no type I, II or III patients and insufficient IV cases to determine sensitivity and specificity. Sensitivity and specificity were determined to be 57.1 and 94.6 % in type V and 92 and 63.6 % in type VI, respectively. We found that 87 % of our patients who tested positive had normal values on discharge.

The Karanth's test is a useful screen for a vitamin B12 deficiency and warrants further evaluation in a larger study population.