ROP

Sepsis screen

Sepsis Screen panel has four criteria: Absolute neutrophil count <1800 per cubic mililitre, Immature to total neutrophil ratio of more than 20% Micro ESR value of more than 15 mm in the first hour Serum CRP level more than 10 mg/L. When two or more criteria are present, the sepsis screen is said to be positive.

Absolute neutrophil count (ANC) For doing absolute neutrophil count or ANC, we do total and differential leucocyte count.

Neutrophils: Whenever there is sepsis and inflammation, there is shift to left in peripheral circulation. By term ‘shift to left’, we mean many immature neutrophils move from the bone marrow to the peripheral circulation. In a peripheral smear, we therefore see mature as well as immature neutrophils. The slide shows picture of different types of immature neutrophils. A mature neutrophil has a multilobed nucleus. While immature neutrophils have a single nucleus that is still not segmented completely. We count both immature as well as mature neutrophils during differential cell count.

For doing absolute neutrophil count or ANC, we do total and differential leucocyte count.

From TLC and DLC we calculate ANC and IT ratio. For calculation of ANC, we take all neutrophils - mature as well as immature - and multiply it with TLC and divide by 100. Take this example. We have a TLC of 10000. In differential count, we find mature neutrophils are 40, immature neutrophils are 10, lymphocytes are 48, and eosinophils are 2. The ANC would therefore be 10000* total neutrophils i.e. (40+10)/100 which equals to 5000. So ANC in this example is 5000. Immature to total neutrophil ratio (IT ratio) Now let us calculate immature to total neutrophil ratio or IT ratio in previous example. The immature neutrophils are 10 in number while total neutrophils are 10 plus 40 that is 50 in no. IT ratio therefore is 20%.

Sepsis screen: Serum CRP can be measured by quantitative method or semi quantitative methods. We have a separate video on how to do CRP test.

Micro ESR: For measurement of Micro-ESR, we take a 75-mm microcapillary, heparinize and filling it with blood. We occlude its one end and suspend it on the wall for one hour. We measure fall in the blood column at one hour. There is another video on it.

Key message: Sepsis screen is a panel of 4 tests namely ANC, IT ratio, micro ESR and S. CRP levels. Presence of two or more criteria makes a sepsis screen positive.