G. Oelk. University of Natural Medicine.
Note that the formula for λ is for an endemic steady state for a virulent disease purchase penegra 100mg on-line prostate anatomy, so it does not imply that R0δ/(δ + d + q) > 1 is the threshold condition for existence of a positive endemic steady state age distribution; compare with [12 discount penegra 100 mg otc prostate oncology specialists los angeles, p. Thus for a very virulent disease, adding a passively immune class to a model increases the average age of attack by the mean period of passive immunity. Solving for R0 in terms of the average period p of passive immunity and the average lifetime L =1/d, we obtain [q +1/(A − p)](1 + pq) (5. In epidemiological terminology, g is the product of the fraction vaccinated and the vaccine eﬃcacy. This vaccination at age Av causes a jump discontinuity in the sus- ceptible age distribution given by s(Av +0)=(1− g)s(Av − 0), where s(Av − 0) is the limit from the left and s(Av + 0) is the limit from the right. The details are omitted, but sub- stituting the steady state solutions i(a) on these intervals into the expression for λ yields R0(d + q) δ(1 − s0) −(λ+d+q)Av −(δ+d+q)Av (5. Given g, Av, and the values for the parameters β, γ, ε, δ, d, and q, the equations (5. Recall that a population has herd immunity if a large enough fraction is immune, so that the disease would not spread if an outside infective were introduced into the population. To determine this threshold we consider the situation when the disease is at a very low level with λ nearly zero, so that almost no one is infected. Thus the initial passively immune fraction m0 is very small and the initial susceptible fraction s0 is nearly 1. If the successfully vaccinated fraction g at age A is large 0 v enough so that −(d+q)Av (5. A similar criterion for herd immunity with vaccination at two ages in a constant population is given in . Intuitively, there are so many immunes that the average infective cannot replace itself with at least one new infective during the infectious period and, consequently, the disease dies out. If the inequality above is not satisﬁed and there are some infecteds initially, then we expect the susceptible fraction to approach the stable age distribution given by the jump solution with a positive, constant λ that satisﬁes (5. The negative signs in the expression for A make it seem as if A is a decreasing function of the successfully vaccinated fraction g, but this is not true since the force of infection λ is a decreasing function of g. For the demo- graphic model in which everyone survives until age L and then dies, d(a) is zero until age L and inﬁnite after age L, so that D(a) is zero until age L and is inﬁnite after age L. Expressions similar to those in this section can be found for a nonconstant population with ρ = q/(1 − e−qL), but they are not presented here. Typically the lifetime L is larger than the average age of attack A ≈ 1/λ, and both are much larger than the average latent period 1/ε and the average infectious period 1/γ. Thus for typical directly transmitted diseases, λL is larger than 5 and γL, εL, γ/λ, and ε/λ are larger than 50. Hence many of the formulas for 0 0 Type I mortality in the Anderson and May book [12, Ch. In sections 7 and 8 we estimate the basic reproduction number in models with age groups for measles in Niger and pertussis in the United States. The initial boundary value problem for this model is given below: ∂S/∂a + ∂S/∂t = −λ(a, t)S − d(a)S, ∞ ∞ λ(a, t)= b(a)˜b(˜a)I(˜a, t)da˜ U(˜a, t)da,˜ 0 0 (6. The boundary ∞ values at age 0 are all zero except for the births given by S(0,t)= 0 f(a)U(a, t)da. The population is partitioned into n age groups as in the demographic model in section 4. The subscripts i denote the parts of the epidemiologic classes in the ith ai age interval [ai−1,ai], so that Si(t)= a S(a, t)da, etc. The total in the four epidemiologic classes for the ith age group is the size N (t)=eqtP of i i the ith group, which is growing exponentially, but the age distribution P1,P2,. Because the numbers are all growing exponentially by eqt, the fractions of the population in the epidemiologic classes are of more interest than the numbers in these epidemiologic classes. Here we follow the same procedure used in the continuous model to ﬁnd an expression for the basic re- production number R0. Substituting s successively, we ﬁnd that s = C /[λˆ ···λˆ ] 1 1 1 i−1 i i−1 i 1 for i ≥ 2, where Ci−1 stands for ci−1 ···c1cˆ1P1. When the expressions for ei and ii−1 are substituted into the expression for i in (6. Now the expressions for i and λ = kb can be substituted into this j=1 j j i i i last summation to obtain n εj bj bj−1 b1 (6. Here the feasible region is the subset of the nonnegative orthant in the 4n-dimensional space with the class fractions in the ith group summing to Pi. In the Liapunov derivative V˙ , choose the α coeﬃcients so that the e terms cancel out by letting i i αn = βnεn/εˆn and αj−1 =(βj−1εj−1 + cj−1αj)/εˆj−1 for αn−1,. Using s ≤ P , n n n j−1 j−1 j j−1 j−1 n−1 1 i i we obtain V˙ ≤ (R −1) ˜b i ≤ 0ifR ≤ 1. The set where V˙ = 0 is the boundary of 0 j j 0 the feasible region with ij = 0 for every j, but dij/dt = εjej on this boundary, so that ij moves oﬀ this boundary unless ej = 0. Thus the disease-free equilibrium is the only positively invariant subset of the set with V˙ = 0, so that all paths in the feasible region approach the disease-free equilib- rium by the Liapunov–Lasalle theorem [92, p. Thus if R0 ≤ 1, then the disease- free equilibrium is asymptotically stable in the feasible region. If R0 > 1, then we have V>˙ 0 for points suﬃciently close to the disease-free equilibrium with s close to P and i i ij > 0 for some j, so that the disease-free equilibrium is unstable. A deterministic compartmental mathemati- cal model has been developed for the study of the eﬀects of heterogeneous mixing and vaccination distribution on disease transmission in Africa . This study focuses on vaccination against measles in the city of Naimey, Niger, in sub-Saharan Africa. The rapidly growing population consists of a majority group with low transmission rates and a minority group of seasonal urban migrants with higher transmission rates. De- mographic and measles epidemiological parameters are estimated from data on Niger. The fertility rates and the death rates in the 16 age groups are obtained from Niger census data. From measles data, it is estimated that the average period of passive immunity 1/δ is 6 months, the average latent period 1/ε is 14 days and the average infectious period 1/γ is 7 days. From data on a 1995 measles outbreak in Niamey, the force of infection λ is estimated to be the constant 0. A computer calculation using the demographic and epidemiological parameter values in the formula (6. Recall from section 1 that the replacement number R is the actual number of new cases per infective during the infectious period. R can be approximated by computing the sum over all age groups of the daily incidence times the average infectious period times the fraction surviving the latent period, and then dividing by the total number of infectives in all age groups, so that 16 1 ε j=1λjsjPj γ + dj + q ε + dj + q R ∼=. This contact number σ is approximated by computing the product of the sum of the daily incidences when all contacts are assumed to be with susceptibles times the average infectious period, and dividing by the total number of infectives. The average age of infection can be approximated in the measles computer simulations by the quotient of the sum of the average age in each age group times the incidence in that age group and the sum of the incidences. This model is plausible because the age distribution of the Niger population is closely approximated by a negative exponential . Using this d value and the fertilities in the Lotka characteristic equation for discrete age groups (4.
Of 63 infected individuals in Peru 50mg penegra sale prostate cancer bone metastasis, 68% were asymptomatic and the highest prevalence occurred among children aged 2 to 4 years buy generic penegra line prostate 84. Examinations have shown malabsorption, atrophy of villi, and crypt hyperplasia (Connor, 1997). In Haiti, 15%–20% of the population examined were found to be carriers of Cyclospora oocysts, but few had diarrhea (Eberhard et al. The Disease in Animals: Cyclospora does not appear to infect animals (see Occurrence in Animals). Source of Infection and Mode of Transmission: Cyclosporiasis is acquired through ingestion of raw fruits and vegetables and contaminated water. A later study, in which 5,552 stool samples were collected from workers on raspberry farms in Guatemala, found infection rates of between 2. A study of the water in domestic containers in Egypt showed that 56% was contaminated with Giardia, 50% with Cryptosporidium, 12% with Blastocystis,9% with Cyclospora, and 3% with microsporidia (Khalifa et al. Using microscopy and molecular biology tech- niques, Sturbaum (1998) identified Cyclospora oocysts in wastewater. Diagnosis: Cyclospora infection is suggested by the patient’s symptoms and by epidemiological circumstances, especially in travelers who have visited endemic areas. The diagnosis is confirmed by detection of the double-walled oocysts meas- uring 8–10 microns in diameter in stool samples. The oocysts are concentrated by formol-ether sedimentation and flotation in Sheather’s sucrose solution. They can be detected by staining, autofluorescence under ultraviolet light, phase contrast microscopy, or polymerase chain reaction (Ortega et al. The stains used most frequently (to make it easier to visualize the organisms and to differentiate them from yeasts) are trichrome stains, Ziehl-Neelsen, Giemsa, safranin with methylene blue, calcofluor white, and auramine phenol. Safranin has been found to be the most effective and appropriate stain for use in diagnostic laboratories (Negm, 1998). Control: Cyclosporiasis can be prevented by applying the classic measures for control of parasitoses transmitted via the fecal-oral route: washing foods that are eaten raw, boiling suspicious water, and washing hands before eating. Treatment of water contaminated with Giardia, Cryptosporidium, Blastocystis, Cyclospora,or microsporidia with chlorine at 4 or 8 parts per million (ppm) or with ozone at 1 ppm showed that ozone was more effective in destroying the parasites, but that it did not totally inactivate Cyclospora or Blastocystis (Khalifa et al. Cyclospora cayetanensis infections in Haiti: A common occurrence in the absence of watery diarrhea. Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals. Ciclosporiasis: estudio clinicoepidemiológico en viajeros con Cyclospora cayetanensis importada. Epidemiology and treatment of Cyclospora cayetanensis infection in Peruvian children. Isolation of Cryptosporidium parvum and Cyclospora cayetanensis from vegetables collected in markets of an endemic region in Peru. Etiology: The taxonomy of the species of the genus Giardia is still controversial. Although in the past many species were described and named according to the host in which they were found—for example, G. Although Lamblia was the original name given to the genus by Lambl when he first described it in 1859, Stiles changed it to Giardia in 1915. The trophozoites are pyri- form and measure 10 µm to 19 µm long, 5 µm to 12 µm wide, and 2 µm to 4 µm thick. Those forms live in the anterior portion of the host’s small intestine, particularly in the duodenum, where they multiply by binary fission. Many of the trophozoites are carried to the ileum, where they secrete a resistant wall and become ovoid cysts measuring 7 µm to 10 µm by 8 µm to 13 µm. They can survive for more than two months in water at 8°C and around one month at 21°C; however, they are sensitive to desiccation, freezing, and sunlight. Solutions of quaternary ammonium recommended for disinfecting the environment will kill them in one minute at 20°C, but normal concentrations of chlorine in drinking water do not affect them. Once ingested, the parasite excysts in the duodenum, divides, and begins to multiply normally. Its prevalence generally ranges from 2% to 4% in industrialized countries, but it may be over 15% among children in developing countries. In the first epidemic, together with Cryptosporidium, it caused 40% of the cases, while in the second epidemic, together with Shigella sonnei, it was responsible for 9% of the cases (Kramer et al. In previously uninfected populations, morbidity rates may be as high as 20% or more of the total population (Knight, 1980). Outbreaks are relatively common in institutions for children, such as orphan- ages and daycare centers. Occurrence in Animals: The infection has been confirmed in a wide variety of domestic and wild mammal species. Surveys from all over the world have found prevalences of 20% to 35% in young dogs; 10% to 15% in young cats; 5% to 90% in calves; 6% to 80% in lambs; 17% to 32% in foals; and 7% to 44% in young pigs (Xiao, 1994). In a study in which feces of 494 dogs were examined for parasites, the infection was detected in 3. High rates of infec- tion have also been found in rats and other rodents, both synanthropic and wild, but whether the agent was G. The Disease in Man: The majority of infections are subclinical (Flanagan, 1992; Farthing, 1996). In symptomatic individuals, the incubation period is generally 3–25 days (Benenson, 1997). The symptomatology consists mainly of diarrhea and bloating, frequently accompanied by abdominal pain. In some persons, giar- diasis may be a prolonged illness, with episodes of recurring diarrhea and flatulence, urticaria, and intolerance of certain foods. These and other allergic manifestations associated with giardiasis disappear after treatment and cure. The manifestations of the disease in dogs and cats are also similar to those in man. However, experimental infections in ruminants produced only mild diarrhea in calves and weight loss in lambs (Zajac, 1992; Olson et al. Source of Infection and Mode of Transmission: Man is the principal reservoir of human giardiasis. The source of infection is feces containing the parasite’s cysts, which often contaminate water. Although the infection in individuals is often self- limited and disappears within a few months, continuous transmission to other hosts in endemic areas ensures the agent’s persistence. The existence of asymptomatic infected individuals and chronic patients, coupled with the cysts’ resistance to envi- ronmental factors, are important factors in the epidemiology. Elimination of cysts can be intermittent and the quantity can vary greatly (Knight, 1980). The most frequent mode of transmission appears to be ingestion of water con- taminated with cysts (Hill, 1993). Direct hand-to-hand or hand-to-mouth transmis- sion of cysts from an infected person to a susceptible person is also common, espe- cially among children, personnel in institutions that care for children or adults, and food-handlers.
Since there are so many important issues that need to be discussed order cheap penegra on-line androgenic hormones birth control, the Module is divided into two parts: Part I order penegra 50 mg visa prostate 32. Female genito-urinary tract Kidney Kidney Ureter Ureter Seminal vesicle Fallopian tube Bladder Ovary Rectum Uterus (womb) Anus Bladder Urethra Rectum Urethra Vagina Anus Diagram 3. Sexually transmitted infections are a Nurses and midwives need to be aware of the role major public health problem, not only because they gender plays in discussions regarding sexual health are a cause of far reaching morbidity, affecting and sexuality in general. In the European Region, This may make us embarrassed about talking about particularly in parts of Eastern Europe, there has sex, or about certain aspects about sex. Cultural sensitivity is important, including Controlling the spread of sexually transmitted awareness of any surrounding issues and language. The mucous membranes lining the vagina broader issues of importance that should be are also potentially more susceptible than those considered by anyone working in sexual health. In addition, menstruation Module 7, Part I Page 201 may increase risk of infection, due to the bleeding, providing an easier route of access for organisms. Similarly, the “passive” or “non-active” partner in a gay relationship is more likely to become infected. Medicine has been principally responsible for attaching deviancy labels to sexual practices decreed as not “normally” practiced. Sexuality and sexual health Nurses and midwives are expected to provide non- judgemental holistic care to their patients; however, sexual health is often overlooked, or only dealt with in the context of illness and disease. Gay and lesbian identity A great variety of pejorative terms have been used to describe individuals who have same-sex partners. Men who have sex with men and identify as being homosexual are usually comfortable with being called Gay. Gay men and lesbian women see their identity and the outward expression of that identity as being central to their sexuality and self-esteem. Neonatal • Urethral discharge chlamydia is most commonly demonstrated as • Mucoid or mucopurulent urethral discharge conjunctivitis and pneumonia. Untreated chlamydia can lead to the • Ectopic pregnancy – the risk increases by seven complications described. Complications in men • Approximately 1% of men with chlamydia will develop reactive arthritis. Chlamydia walking is currently diagnosed using laboratory tests on • Painful movement as a result of tenosynovitis swab and urine samples taken from the patient. Methods of treatment Uncomplicated infection Contact tracing of women and asymptomatic Azithromycin 1 g as a single dose or Doxycycline men 100 mg two times per day for seven days. All sexual partners over the six months preceding the (Doxycycline is cheaper than Azithromycin, but diagnosis, or the last sexual partner if the most has a 20% chance of causing gastro-intestinal recent sexual contact was more than six months disturbances and occasionally photosensitivity; prior, should be traced. These treatments have a less than 95% efficacy, so Follow-up pregnant women should be followed up carefully Patients diagnosed with chlamydia should be seen to ensure there has been no treatment failure. In patients treated with treatment, sexual intercourse should be avoided for Erythromycin, a second test should be taken after one week after treatment. Thesting for chlamydia should be offered to the • Ensure that contact tracing has taken place if the following groups: person has arranged to contact their partner Module 7, Part I Page 205 Gonorrhoea themselves. Gonorrhoea infects the Nursing care mucous membranes of the urogenital tract, oro- See Appendix 4. Modes of transmission Sexual transmission Through vaginal and insertive and receptive anal sex. Untreated opthalmitis may lead to conjunctival destruction, corneal ulceration and blindness. Treatment is with ceftriaxone 50 mg/kg (max 125 mg) in a single intramuscular dose. In many industrialized countries, there has been an overall decline in the incidence of gonorrhoea over the last decade. Reported gonorrhoea in Sweden and Norway has declined from 10 000 cases each in 1981 to almost zero in 2000. Reports from France and the United Kingdom in 2000 have shown an increase in gonorrhoea since 1997, particularly in men, with suggestions of an increase in high risk Page 206 Module 7, Part I sexual behaviour, especially in gay men. In men: Rectal gonorrhoea in men is associated with It is reported that the burden of gonorrhoea in receptive anal sex. It is most commonly developed countries tends to fall on deprived, inner asymptomatic, but clinical features may include: city populations. Over 90% of gonococcal • Menorrhagia infections in the pharynx are asymptomatic and • Mucopurulent cervical discharge have a spontaneous cure rate of nearly 100% after • Xervical erythema 12 weeks of infection. Urethral gonorrhoea; incubation is 1–14 days or • Ectopic pregnancy (see previous notes). It is treatable • Sysuria with antibiotics, but may require surgery to drain • Less commonly, epididymal tenderness or swelling the abscess. It occurs Rectal infection in women can occur after receptive within 7 to 30 days after transmission. Features anal sex but is also associated with perineal include acute arthritis, tenosynovitis, dermatitis, contamination with cervical secretions where no or a combination of the three. It is estimated that 35– 50% of women with gonococcal cervicitis also have Complications in men infected rectal mucosa. Rectal gonorrhoea in • Epididymitis, a unilateral testicular pain and women is usually asymptomatic. Male urethral swab • 15–19 year olds at particularly high risk • Low socioeconomic status • Past history of gonorrhoe • Early onset of sexual activity Prognosis Gonorrhoea generally remains localised to the initial sites of infection. The complications of gonorrhoea leading to serious morbidity are commoner in areas where access to diagnosis and treatment is more difficult. Diagnosis Diagnosis is made by identification of the organism Neisseria gonorrhoea at the site of infection Diagram 6. Female urethral swab through: • Microscopy; direct visualization of Gram stained specimens allows diagnosis of gonorrhoea when Gram negative diplococci are seen within polymorphonuclear leucocytes. Rectal gonorrhoea is more likely to be diagnosed through microscopy if a proctoscope has been used to collect the sample. Speculum examination and tests Worldwide, resistant strains have developed to penicillins and quinolones. Antibiotics for Swab Cervix Cervical swab being taken gonorrhoea should be selected to clear over 95% of infection in the local area. Ceftriaxone has been used worldwide effectively as a single dose with as yet no noted resistance. Speculum Co-infection with chlamydia trachomatis Up to 40% of adults with genital gonorrhoea infection also have chlamydia. Treating for both infections simultaneously after a diagnosis of Cervical swab gonorrhoea is made is recommended. Cervical smear Screening Thesting for gonorrhoea should be offered to the following groups: Methods of treatment • patients with signs or symptoms attributable to Uncomplicated genital infection gonorrhoea; Ceftriaxone 250 mg intramuscularly as a single • individuals attending sexual health clinics; dose; Ciprofloxacin 500 mg as a single oral dose; • anyone diagnosed with another sexually Ampicillin 2 g or 3 g plus Probenecid 1 g orally as transmitted infection; and a single dose in regions where penicillin resistance • sexual partners of patients with gonorrhoea. Ceftriaxone 250 mg intra- urethral infection muscularly as a single dose; Cefotaxime 500 mg See Appendix 2 for partner management. Other Eastern European countries including Module 7, Part I Page 209 Contact tracing of men and women with asymptomatic infection and infection at other sites Trace all sexual partners in the three months preceding the diagnosis. Follow-up Patients diagnosed with gonorrhoea should be seen again after treatment has been completed in order to assess efficacy of treatment.
Initially cheapest generic penegra uk mens health 042013 chomikuj, body iron stores fall and this is reflected in decreasing serum ferritin levels penegra 50 mg line prostate medication. There can be confounding effects from lymphoma, liver disease, infec- tion, thalassemia, age, and sex. In the second stage, the lack of sufficient iron supply is reflected in a low serum iron level, decreased transferrin saturation, and increased erythrocyte protoporphyrin levels. Confounding effects for serum iron include alcoholism; infection; malignancy; deficiencies of B6, B12, folate, and vitamin C; and viral hepatitis. For total iron-binding capacity, the 162 Part One / Principles of Nutritional Medicine confounding effects include infection, protein-calorie malnutrition, alcoholic cirrhosis, malignancy, pregnancy, and viral hepatitis. Confounding effects include infection, B12 and folate deficiency, chronic dis- eases, hemoglobinopathies, sex, and altitude. However, as with B12, it is important to remember that values of ferritin, for example, in the low-normal range may be associated with some measure of impaired energy or cognitive performance. There is no completely satisfactory test for zinc status, and the prolif- eration of static and functional tests over the years is adequate testimony to this fact. A low serum zinc level is a late marker of zinc deficiency, and in fact, all tests of tissue or tissue fluid level (including red and white blood cells, hair, nails, saliva, sweat, and urine) have marked limitations. Zinc-loading tests are not routinely performed, and functional tests of zinc-related enzymes or proteins (e. We may still conclude that the best way to test for zinc deficiency is through a therapeutic trial. The assessment of copper levels in the blood is complicated by the fact that more than 90% of circulating copper is bound to ceruloplasmin, which is an acute-phase reactant whose level will be influenced by inflammation and a number of pathologic conditions. Pregnancy, hormone replacement therapy, and the contraceptive pill all tend to raise copper levels, which, even under normal circumstances, tend to be higher in women. Red blood cell superoxide dismutase is a potentially useful but not widely available test. Lymphocyte manganese superoxide dismutase can be affected by a number of disease states and inflammation. There is no reliable method of chromium estimation, and as with other micronutrients, the best test is often a therapeutic trial. Thus glu- cose, insulin, and lipid values should be monitored before and after supple- mentation. Plasma selenium gives a fairly good guide to short-term sele- nium status and whole-blood or erythrocyte selenium to longer-term status. The urinary iodine test is enjoying a revival of interest because of the growing realization that there is a return of widespread iodine deficiency in the community. With respect to the first problem, split hair samples were sent to six laboratories in the United States, and the results were compared. For many of the trace nutrients, however, one can find evidence to support good correlations with other parameters of nutrient status. There is a good correlation between hair and plasma selenium levels in healthy children. Accumulation of minerals in hair involves very different processes from those that are reflected, for example, in erythrocyte mineral levels. Hair min- erals accumulate over time, and their concentrations are influenced by endocrine and dietary factors. Hair zinc levels increased in experimental ani- mals when the protein/carbohydrate ratio increased. Practitioners who use metabolic typing systems 164 Part One / Principles of Nutritional Medicine must conduct their own research projects to investigate these possibilities further. External contamination of hair with elements, such as copper, is a prob- lem that cannot be completely eliminated by laboratory processing. It is particularly useful in alerting one to the possibilities of toxic metal accu- mulation and in identifying trace nutrient deficiencies (e. I have been impressed with the consistency of the profiles, the correlation of low nutrient levels with other, corroborative tests, and the response of hair levels to mineral supplementation. Thyroid Function Of all the endocrine systems, the thyroid merits special attention because of the significant incidence of thyroid problems and also the far-reaching effects of even minimal thyroid dysfunction. Hypothyroidism is not an all- or-nothing phenomenon, and it is becoming increasingly clear that thyroid failure encompasses a spectrum of dysfunction from overt myxoedema to subtle problems of cellular responsiveness manifesting in ill-defined clinical ways. To do justice to this variety of clinical presentation, testing methods must be appropriately sensitive. Further supporting evidence can be obtained from the temperature recording method described previously. The urinary level of triiodothyronine may prove a good indicator of sub- tle thyroid dysfunction,50 and the urinary iodine level should not be forgot- ten as part of the overall thyroid testing. Results of other tests, such as measurements of total cholesterol and crea- tine phosophokinase, may be abnormal, but they lack specificity. Fried R: The psychology and physiology of breathing, New York, 1993, Plenum Press. Brostoff J, Gamlin L: The complete guide to food allergy and intolerance, London, 1989, Bloomsbury Publishing. Tintera J: The hypoadrenocortical state and its management, N Y State J Med 35(13), 1955. Shibata K, Matsuo H: The relationship between protein intake and the ratio of N methyl -2-pyridone and N methylnicotinamide, Agric Biol Chem 52:2747-52, 1988. Therada A, Nakada M, Nakada K, et al: Selenium administration to a ten year old boy receiving long term parenteral nutrition—change in selenium concentration in blood and hair, J Trace Elem Med Biol 10:1-5, 1996. Gershoff S, McGandy R, Nondastuda A, et al: Trace minerals in human and rat hair, Am J Nutr 30:868-72, 1977. Laboratory investigations are used to predict disease and to confirm a working diagnosis in persons with suspected disease. Biochemical testing covers a wide spectrum of investiga- tion and includes both simple and sophisticated testing methods. Body chemistry is constantly shifting in accord with biorhythmic cycles, environmental challenge, and dietary change. Because these variables can affect the results of biochemical tests, it is wise to schedule tests so that these conditions, including time of day and season, are parallel. It is essential to put test results within the context of the whole clinical picture. This chapter focuses on how measurement of various chemicals can serve as diagnostic markers. Particular attention is paid to how these various lab- oratory assessments can be used as a guide to disease prevention and patient care. The assessments detailed describe those test most frequently requested by practitioners.