In nutriverse/nutricheckr: Tools for Nutrition Assessment and Analysis

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library(nutricheckr)

Determining iron storage status

Iron storage status can be determined using serum ferritin concentration. This package includes a set of functions used in determining iron storage status:

1. Functions that identify inflammation status based on the levels of acute-phase proteins;

2. Functions taht correct serum ferritin concentration values based on the inflammation status; and,

3. Functions that categorise iron storage status based on the corrected serum ferritin concentration for a specific target group (either under 5 years old or 5 years and over).

These functions were designed and developed based on iron deficiency status determination described in:

Namaste, S. M., Rohner, F., Huang, J., Bhushan, N. L., Flores-Ayala, R., Kupka, R., Mei, Z., Rawat, R., Williams, A. M., Raiten, D. J., Northrop-Clewes, C. A., & Suchdev, P. S. (2017). Adjusting ferritin concentrations for inflammation: Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project. The American journal of clinical nutrition, 106(Suppl 1), 359S–371S. https://doi.org/10.3945/ajcn.116.141762

Inflammation status

Inflammation, and its different stages, can be identified based on the availability of acute-phase proteins - one of either c-reactive protein (CRP) or α1-acid-glycoprotein (AGP), or both. The detailed classification of inflammation status based on combination of both CRP and AGP apply the following cut-off values:

| Inflammation Categories | Cut-off Points | | :--- | :--- | | Incubation | CRP > 5 mg/L & AGP <= 1 g/L | | Early convalescence | CRP > 5 mg/L & AGP > 1 g/L | | Late convalescence | CRP <= 5 mg/L & AGP > 1 g/L |

If only either CRP or AGP is available, the cut-off values for determining inflammation are shown below:

| Type of Protein | Cut-off Points (inflammation) | | :--- | :--- | | CRP | CRP > 5 mg/L | | AGP | AGP > 1 g/L |

These conventions are used in the set of functions to determine levels of inflammation. For example, to determine inflammation status of an individual with a CRP value of 6 mg/L but with no AGP information available, we use:

detect_inflammation_crp(6)

which gives:

detect_inflammation_crp(6)

Then, in the second stage, based on the inflammation status result from step one, there is a specific commend for ferritin value correction and each command will provide the new vector called ferritin_corrected with the fixed ferritin value. correct_ferritin: use this command if the first stage of identification of inflammation was performed based on both acute-phase proteins (CRP and AGP) correct_ferritin_crp: If the inflammation status of your data was identified by CRP protein alone, use this command for correction of ferritin value. This command will correct each observation ferritin value respective to their inflammation status. correct_ferritin_agp: If the identification of inflammation status was performed by the AGP protein alone, use this command. This command will correct the ferritin value based on the respective observation inflammation status. correct_ferritin: If your data observation inflammation status was four-category outputs as both CRP and AGP protein identified those, use this one. Based on each observation inflammation status, each observation ferritin values were corrected.

If the inflammation status was identified based on combination of both CRP and AGP proteins, the ferritin correction values are performed as multiply with the correction values provided in the below table.

| **inflammation Categories** | **Correction Values** |
| :--- | :--- |
| Incubation | 0.77 |
| Early convalescence | 0.53 |
| Late convalescence | 0.75 |

If only either CRP or AGP proteins is applied, the different correction value are applied based on type of protein as mentioned in the below table.

| **Type of Protein** | **Correction Values** |
| :--- | :--- |
| CRP | 0.65 |
| AGP | 0.72 |

In the final stage, based on the corrected ferritin value and specific target age group, there were particular commends to perform iron storage status diagnosis for individual observation. detect_iron: If your data had already corrected ferritin value based on either acute-phase protein or both, use this command. Based on the age group of the individual observation and its inflammation status, this will generate the new vector called iron_storage and which contains the binary outcome of iron storage status ("deficiency" and "no deficiency"). This command works for both under 5 and over 5 years old. detect_iron_quali: If the inflammation status was identified based on the qualitative report (such as self-reporting from the survey), use this commend for iron status identification. This will also generate the new vector called iron_storage and which contains the binary outcome of iron storage status ("deficiency" and "no deficiency"). But, this can only apply to the under 5 years old children population.

The cut-off points value for identification of iron storage category is mentioned in the below table.

| **Population** | **No Deficiency** |  **Deficiency** |
| :--- | :--- | :--- | :--- |
| < 5 year old (both sex) | Ferritin < 12 | Ferritin >= 12 |
| >= 5 years old (Male) |   Ferritin < 15   |  15 >= Ferritin >= 200 |
| >= 5 years old (Female)   | Ferritin < 15 | 15 >= Ferritin >= 150 |

If the inflammation status was identified based on qualitative inforomation, the cut-off point is applied to original ferritin value as < 30 micrograms per liter (µg/l) unit is consider as deficiency status.

nutriverse/nutricheckr documentation built on April 1, 2022, 7:44 p.m.