Nitroblue tetrazolium test in children with malnutrition

The immune system in children with malnutrition--a systematic review

Background

Malnourished children have increased risk of dying, with most deaths caused by infectious diseases. One mechanism behind this may be impaired immune function. However, this immune deficiency of malnutrition has not previously been systematically reviewed.

Objectives

To review the scientific literature about immune function in children with malnutrition.

Methods

A systematic literature search was done in PubMed, and additional articles identified in reference lists and by correspondence with experts in the field. The inclusion criteria were studies investigating immune parameters in children aged 1–60 months, in relation to malnutrition, defined as wasting, underweight, stunting, or oedematous malnutrition.

Results

The literature search yielded 3402 articles, of which 245 met the inclusion criteria. Most were published between 1970 and 1990, and only 33 after 2003. Malnutrition is associated with impaired gut-barrier function, reduced exocrine secretion of protective substances, and low levels of plasma complement. Lymphatic tissue, particularly the thymus, undergoes atrophy, and delayed-type hypersensitivity responses are reduced. Levels of antibodies produced after vaccination are reduced in severely malnourished children, but intact in moderate malnutrition. Cytokine patterns are skewed towards a Th2-response. Other immune parameters seem intact or elevated: leukocyte and lymphocyte counts are unaffected, and levels of immunoglobulins, particularly immunoglobulin A, are high. The acute phase response appears intact, and sometimes present in the absence of clinical infection. Limitations to the studies include their observational and often cross-sectional design and frequent confounding by infections in the children studied.

Conclusion

The immunological alterations associated with malnutrition in children may contribute to increased mortality. However, the underlying mechanisms are still inadequately understood, as well as why different types of malnutrition are associated with different immunological alterations. Better designed prospective studies are needed, based on current understanding of immunology and with state-of-the-art methods.

Low protein diets improve survival from peritonitis in guinea pigs

Enteral diets with different protein content were tested to determine their effect on outcome in a model of protracted bacterial peritonitis. Hartley guinea pigs were provided with gastrostomies, and 1 week later, osmotic pumps were implanted into the peritoneal cavity to allow for continuous release of live bacteria over the course of 1 week. Three days after pump implantation, the animals began receiving isocaloric enteral diets that contained 5%, 10%, 15%, or 20% of total calories as protein. After 2 weeks of observation, the survivors were killed. All animals lost weight during the 2-weeks period, but there was no difference in weight lost. Nitrogen balance correlated with dietary protein. The mortality rate was significantly higher in the groups that received 15% and 20% of total calories compared with the group that received 5% (p less than 0.05). Although dietary protein in the 5% group was insufficient for meeting the nutritional needs of the animal, survival was best in this group. Possible explanations are that protein restriction in this model may either augment host defence or impair bacterial virulence.

Bacteremic infection and malnutrition in patients with solid tumors: investigation of host defense mechanisms

Eighty-five patients with solid tumors without neutropenia were studied in order to determine host characteristics associated with bacteremic infection. Twenty patients without neoplastic disease who had bacteremia served as controls. Bacteremia frequently occurred in patients with tumors of the gastrointestinal and urinary tract, who were over 51 years of age, and had evidence of malnutrition. Peripheral blood lymphocyte dysfunction in vitro was commonly noted in infected patients with cancer. Polymorphonuclear leukocyte (PMNL) dysfunction was common in older bacteremic patients with and without cancer. The PMNL abnormality appeared to be cellular, it was not corrected with use of pooled normal serum, and was manifested by poor uptake of the assay organisms.

An appraisal of the nitroblue tetrazolium reduction test

The available literature on the nitroblue tetrazolium reduction test is reviewed. The mechanism of this test is poorly understood. There are two basic methods of performing the test, namely, the stimulated and the spontaneous methods. However, the test procedure has not been standardized, and numerous modifications have ensued resulting in a number of technics. The stimulated test has proved to be valuable for screening patients or carriers with chronic granulomatous disease of childhood. It is one of the useful tests in studying neutrophil dysfunction. On the other hand, extensive accumulated data indicate that this test, be it stimulted or spontaneous, cannot be relied upon as an absolute test to differentiate bacterial from nonbacterial infectious disease as there have been numerous false-positive and false-negative results. When this test is used, the result should be interpreted in the context of other laboratory test results and the clinical picture of the patient. Preliminary data indicate that in certain diseases, if the initial test is positive in a particular patient, it may be useful as one of the follow-up tests to ascertain the activity of the disease process.

Leucocyte function in children with kwashiorkor

A study of leucocyte response to infection, polymorphonuclear leucocyte chemotaxis and bactericidal activity, and nitroblue tetrazolium (NBT) reduction in children with kwashiorkor was undertaken and compared with a control group. The results show that total leucocyte counts were depressed in children with kwashiorkor, and lymphopenia was not infrequent. NBT reduction was normal. Abnormal polymorphonuclear leucocyte chemotaxis and bactericidal activity, though frequently found in children with kwashiorkor, was shown to be dependent on infection and not on protein depletion per se. Therefore, apart from some impairment of leucocyte mobilization in the presence of infection, the qualtiy of polymorphonuclear function, as determined by the above techniques, appears to be normal in kwashiorkor.