The Two‐Factor Method—A New Approach to Categorizing the Clinical Stages of Malnutrition in Geriatric Patients
2002-12-01

To the Editor: Malnutrition is of high clinical and prognostic significance in older patients.1 Its prevalence is associated with elevated mortality rates (up to 30% in geriatric patients).2 The incidence of malnutrition is higher in patients receiving clinical care and can be described as a complication of clinical care. Often, it is not diagnosed or treated. There is no standard European or other international consensus for the definition and categorization of the degree of severity of malnutrition in geriatric patients at the present time.3 Serum albumin, serum prealbumin, an ultrasound cross-section of the musculus femoris rectus, and the angle phi are discussed as objective parameters for the assessment of malnutrition. Taking these parameters into account in comparison with the clinical assessment of malnutrition based on subjective global assessment (SGA) led to the development of the 2-F method model (two factors—albumin and muscle cross-section). The 2-F method categorizes subjects—irrespective of age and sex—into three groups (no malnutrition, risk of malnutrition, and manifest malnutrition), based on chemical laboratory and ultrasound values. The test results presented pertain to 124 consecutively admitted geriatric patients at a university training hospital specializing in geriatrics. The aim was, with the assistance of a regression analysis of recorded clinical, chemical laboratory, ultrasound, and bioimpedance test values, to derive informative parameters for the diagnosis of malnutrition in comparison with SGA and, subsequently, via a discriminance analysis for SGA, to develop a method for categorizing degrees of malnutrition based on objective parameters. When the patients were admitted, the clinical assessment of nutritional status based on SGA was documented and the data pertaining to albumin, prealbumin, ferritin, soluble transferrin receptor, hemiglobin, hematocrit, lymphocyte count, age, place of admittance, and primary disorders were recorded. In the second step, two specially trained physicians performed an ultrasound muscle cross-section in the mid-thigh region (musculus rectus femoris) on the patients in a lying position, and bioimpedance was measured by calculating the angle phi and the body cell mass (BCM) using the soft-tissue method. In the third step, the acquired data were statistically evaluated in the context of the SGA assessment (using JMP 4.0 software). From this, a two-factor model was derived, based on which the degree of malnutrition can be analogously and clearly categorized, as in the SGA assessment. A comparison of the results of the log regression analysis of the SGA grading in dependence on the five parameters (albumin, prealbumin, muscular ultrasound, body cell mass (BCM), angle phi) showed that only two parameters are of informative value for the assessment of malnutrition (n = 112 patients): albumin and the ultrasound muscle cross-section. (Muscular ultrasound and BCM were logarithmized (log10) because they demonstrate an asymmetrical distribution.) After stepwise regression, the P-values were .0005 (95% confidence interval = 0.72–2.45) for albumin and P≤ .0001 (95% CI = 3.25–7.36) for muscular ultrasound if these were the only two parameters taken into consideration (n = 116 patients). The cross-validation via jackknife (SPSS, version 10 for Windows, SPSS Inc., Chicago, IL) leads to the same categorization as the discriminance analysis, which means that the categorization can be viewed as stable. Although prealbumin, BCM, and angle phi make clear changes in dependency on nutritional status evident, only prealbumin would be capable of distinguishing manifest malnutrition patients from the two other groups. BCM and angle phi can only deliver trends, although no sharp divisions exist between the three nutritional groups. Prealbumin, BCM, and angle phi do not provide any additional useful information for the group of patients tested. A graph can be created from the factors of albumin and muscular ultrasound (see Figure 1) that simply and logically establishes the degree of malnutrition without further clinical data. This categorization for 71 (61%) of the test group of patients was consistent with the SGA. It was also evident that the results for the test group of patients were not dependent on age or sex. Three-stage categorization of malnutrition according to the 2-F method with albumin and muscular ultrasound. The data obtained from albumin and muscular ultrasound measurements are entered in the graph, permitting immediate allocation to the three groups (gray = normal nutritional status, white = risk of malnutrition, black = manifest malnutrition). The 2-F method for the assessment and categorization of malnutrition in geriatric clinic patients is objective, reproducible, comprehensible, and inexpensive. The necessary tests can be implemented in less than 5 minutes, the results can be simply and quickly compiled in a graph, and the categorization is immediately evident. It records visceral protein (albumin), a subjective physician/clinical assessment (SGA), and objective measurements of somatic protein reserves (muscular ultrasound). This provides clinical physicians with an assessment method based on malnutrition-relevant measurement parameters for the clinical assessment of the malnutrition status of geriatric patients. The result is a fast and clear categorization of malnutrition. One surprising aspect is that bioimpedance measurements are not capable of differentiating between the groups. This could indicate that this measuring procedure is suitable for recording more-precise data on individual progress during therapy.