We thank Dr. Ajay Kumar and Drs. Srinivas Murki and Anil Narang for giving us an opportunity to provide more details regarding our paper(1).

Two main issues have been raised by Dr. Ajay Kumar regarding our article(1). The first issue pertains to procedural lacunae and second to statistical lacunae. Regarding the first, for preparing potassium dichromate solution, 2.0 g of potassium dichromate was weighed on an accurate and sensitive balance and hence an accurate chemical balance is required. Potassium dichromate has the advantages of being inexpensive, very stable in solution and available in sufficiently pure form for preparing standard solutions(2,3). Once prepared the diluted solutions were used over whole of study period which lasted for approximately three months. During this period no color change was observed in solutions. Plasma colar and diluted potassium dichromate solution colors were compared against white paper background in day light. Plasma color always matched with one or the adjacent potassium dichromate solutions so there cannot be any difficulty and none was encountered by the analyzer while comparing the color index. Nothing was required to be done to approximate the density of plasma to that of potassium dichromate solution as we had compared only the colors, not the density of the two solutions. Another important substance which imparts yellow color to the plasma is carotene. In the presence of carotenemia, the icterus index is increased and it does not truly reflect the bilirubin content. High concentrations of carotene are found in hypothyroid states, in patients with hyper-lipidemia associated with diabetes or with chronic renal disease(4). None of these conditions were present in subjects of our study.

Regarding statistical lacunae, the range of serum bilirubin was 7.4 mg/dl to 23.0 mg/dl and range of color index was 40-120. It was mentioned in the original manuscript but on suggestions of reviewers, only mean and standard deviations were included in the final manuscript. All the values of serum bilirubin and color index were plotted on graph paper and it was observed that all the values are clustered around the regression line equally on both sides having a coefficient of correlation (r) = 0.97; which is statistically a good correlation. 95% confidence interval of serum bilirubin at different levels of color index are shown in Table I.

We are not in agreement with the comments of Drs. Srinivas Murki and Anil Narang that the present study does not seem to obviate the need for any of requirements, i.e. simplicity and reproducibility.

As earlier stated, the solutions of potassium dichromate are indefinitely stable(2,3) and dilutions are not required to be made daily. To compare, we will require 20 test tubes which are not very costly, are easily available and are not required to be changed frequently as solution is stable. We had mentioned that no inter or intra observer comparison was carried out for the naked eye color index estimation. We agree that blinding, inter and intra observer measurements can strengthen the study. However, 95% confidence limits for each of the color indices is shown in Table I. Cost of one capillary ranges from Rs. 1.20 to Rs. 1.50, which is easily affordable. Centrifuge machine required for centrifugation is a multipurpose instrument commonly available in laboratories for performing various tests.

As amount of blood required of Diazo method was 3 ml, femoral puncture was done with great caution and we did not encounter any complication during the study. However, it could be avoided. This study was conducted since the blood volume required for standard methods is large and micromethods are not available in our instituion.

Table I - Mean and 95% CI Serum Bilirubin Values at Different Color Indices

1. Singh M, Batish MH, Singh M., Singh K, Locham KK, Garg R. Correlation of plasma color index with serum bilirubin in neonatal jaundice. Indian Pediatr 2001; 38: 278-280.

2. Day Jr RA, Underwood AL. Potassium dichromate - Application of oxidative reduc-tion titrations. In: Quantitative Analysis, 5th edn. New Delhi, Prentice Hall of India Private Ltd., 1988; p 327.

3. Skoog DA, West DM. Application of oxidative reduction tritrations - Potassium dichromate. In: Fundamentals of Analytical Chemistry, 3rd edn. California, Holt Rinehart Winston, 1975; p 349.

4. Mcmurray WA, Gowenlock AH. Vitamins, In: Varley’s Practical Clinical Biochemistry, 6th edn. Oxtord, Heinemann Medical Books, 1988; p 899.