Individual levels stratified

Figure 1. Individual levels of PAH-DNA adducts in samples with detectable adducts stratified by fire fighting activity (FF) and charcoal-broiled food consumption (CBF). Mean adduct levels are indicated in each group. (Reproduced with permission from Ref A. Copyright 1990, Oxford University).

Figure 2. Individual levels of PAH-DNA adducts stratified by number of exposure sources (fire fighting, smoking, or CB food consumption).

The NKF-K/DOQI guidelines stratify CKD from stage 1 at the mild end of the spectrum to stage 5, kidney failure or GFR less than 15 mL/min/m. Although the cut-off levels between the stages are arbitrary, the process may allow for consistency in prevalence reporting for epidemiological studies and also focused treatment schedules for individual patients (see Table 45-6). 

Class stratification marks another level of hierarchical organization and involves the use of status, rather than kinship, to determine an individual s position in society. Stratified societies have fixed classes or levels of social organization, ranging in many cases from slaves at the bottom to kings and queens at the top. Social classes -something like the caste system that existed in South Asia - define your place in life and death, where you can live, your occupation, your potential marriage partner, and where you are buried. Status in a stratified society is determined by the class into which you are bom. 

Bellinger and Needleman (2003) reanalyzed their earlier cohort data, specifically stratifying the outcomes of the psychometric tests and dose—response strengths for 24-month PbB levels into those <10 pg/dl (N = 48) and those S 10 pg/dl. These authors reported that the dose—response slope, IQ loss versus PbB increase, was threefold steeper at PbB <10 pg/dl than for blood Pb values at 10 units or higher. This curvilinear relationship across the dose—response spectrum at lower versus higher dose has been documented in other individual and aggregated studies noted below. 

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