Age 3 years and older: faces scales, Pieces of Hurt Th e VAS and the NRS are presumed to re quire the child to have some competence in seriation (putting things in order) and mag- nit ude estimation, as well as counting in the case of the NRS. Th ese skills are not well deve loped in most children before age 6 or 7. By contrast, faces scales, in principle, require only matching one \200\231s own state of distress to one of the pictures, without necessari ly hav- ing to estimate quantities along a numerical or spatial dimension (Champion et al., 1998 ). Th ese limited cognitive demands make faces scales more suitable for children of p reschool age than the VAS and NRS. Other simplifi cations of pain intensity scales adapted for pre- school-aged children have been proposed but not yet adequately studied. For example, one could ask whether the child has any hurt (using a word the child knows). If the answer is no, the score is 0. If yes, t hen a modifi ed faces scale comprising three faces \200\224small, medium, and large pain in tensity \200\224is administered (von Baeyer et al., 2011 , 2013 ). Th e faces would be redr awn to suit the prefer- ence and comprehension of young children. Interpretation of self-reported pain intensity scores In general, comparisons of pain inten sity scores across time within an individual are more valid than comparisons of such scores across diff erent children. In other words, the score 8/10 might mean some- thing quite di ff erent to one child than to another. However, within individuals, an increase or decrease over time can be interpreted as an index of the effi cacy of pain management eff orts. Dozens of faces scales have been created; of these, three have emerged as the predominant a nd best validated choices (Tomlinson et al., 2010 ): the Faces Pain Scale \200\223Revised ( FPS-R; Figure 36.2 ; < http://www.iasp-pain.org/FPSR >) (Hicks et al., 2001 ); the OUCHER ( Beyer et al., 1992 ; < http://www.oucher.org >); and the Wong-Baker FACES Pain Rating Scale (Whaley and Wong 1991 ; < http://www.wongbakerfaces.org >). Each of these was developed Despite these limitations in interpretation of self-report scores, there have been eff orts to create and validate algorithms governing analgesic administration by pain scores, where by drugs and dosages are selected following rules based on the intensity and duration of pa in (e.g. Falanga et al., 2006 ). Data on eff ects of such algorithms are mixed. 100 n e r d 80 l i h c 60 f o e g a t n e c r e P 40 20 Children \200\231s pain intensity scores do not always make sense to adults. Children somet imes assign high scores to their pain inten- sity when they are assumed to be in no or litt le pain (e.g. before a needle or operation); at other times they assign low scores when the y are believed to be in severe pain. Caregivers might not under- stand the numerous possibl e reasons for these discrepancies. 0 0 2 4 6 8 10 12 Age (years) Pieces of hurt Faces scales Visual analog scales Numerical scales \231 Young children might not understand the scale, so they oft en use a variety of irrel evant strategies to answer the caregiver \200\231s question (von Baeyer et al., 2009 ). For example, up to one-third of children aged 3 and 4 use only the bottom and top of pain scal es, treating them as dichotomous (pain or no pain) rather than graded scales. Figure 36.2 Estimated percentage of children who are able to provide valid self- report of pain intensity as a function of age. Adapted from Lara Spagrud et al., Children \200\231s S elf-Report of Pain Intensity: Th e Faces Pain Scale \200\223Revised, American Journal of Nu rsing , Volume 103, Issue 12, pp. 62 \200\22364, Copyright 2003 C. L. von Baeyer, with p ermission of the author. Th is \201 gure has been reproduced with permission of the Inter national Association for the Study of Pain (IASP). Th e \201 gure may not be reproduced for any other purpose without permission. \231 A variety of cognitive skills are required for accurate use of self- report scales, as cataloged by Besenski et al. ( 2007 ). Th ese skills CHAPTER 36 self-report: the primary source in assessment after infancy 373 develop gradually, with a majority of children but not all acquir- ing the necessary skills by age 7 or 8. of postoperative pain in children aged 3 to 7 years (Beyer et al., 1990 ), the median corre lation between concurrent scores on an observational measure, the Children \200\231s Hospit al of Eastern Ontario Pain Scale (CHEOPS), and the Oucher was r = 0.41, and between the CHE OPS and a mechanical VAS it was r = 0.35. Similarly, in a study of 5-year-olds undergoing i mmunization injections (Cassidy et al., 2001 ), Spearman correlations between a faces pain score and the CHEOPS during and aft er the needle were r s = 0.47 and r s = 0.33. In other words, in many cases the self-report scores were at variance with observers \200\231 scores on a well-established behav- ioural measure. \231 Children sometimes locate their pain within a body part, not in themselves, thus in a sense separating themselves from the pain and producing lower than expected pain ratings (Wennstrom and Bergh, 2008 ). \231 Adults have experience with a variety of mental models (Halford, 1993 ) for rating q uantities. Th ey have encountered volume con- trols to adjust loudness; thermometers, weigh t scales, and rul- ers; and star systems for rating quality of hotels or movies. Young chil dren have far less experience with such mental models, though they have encountered stairca ses (low to high steps), toys that can be placed in order from small to large, and pictures of small and larger numbers of objects. Such analogies can be useful in measurement of pai n intensity, as for example in the Pieces of Hurt tool. Th e modest observer \200\223child concordance, and the lack of a gold standard measure of pain intensity, lead to a dilemma for clinicians. Th ere is no validated way to combine and balance estimates of pain intensity from diff erent sources, nor to adjust self-report sco res to bring them into line with observation and knowledge of the clini- cal context. Yet s everal studies have shown that nurses oft en do so: they alter patients \200\231 self-repor ted pain scores when recording them in medical charts (Pasero and McCaff ery, 2011 , p. 18) , or fail to ask for self-report and substitute their own informal rating. Pasero and McCaf f ery suggest that when patients \200\231 self-report scores are not accepted and acted upo n, \200\230chaos quickly ensues \200\231 (p. 21) because each clinician has diff erent imp ressions, standards, and biases in judging patients \200\231 pain. On the other hand, somet imes self-reports confl ict with other sources of information (see case example). In this c ase example, much additional information is required beyond the simple pain intensity score . \231 Children probably have a very diff erent understanding of the top scale anchor (a hy pothetical maximal level of pain) than adults, as children have less direct and vicarious e xperience of severe pain. Moreover, young children might not be able simultane- ously to th ink of their own pain and a hypothetical maximal pain for comparison of the two, a characte ristic termed \200\230centra- tion \200\231 in Piaget \200\231s accounts of cognitive deve lopment (Gelman and Baillargeon, 2003 ). \231 Children might be inclined to deny or minimize their pain because they believe, accu rately or not, that something bad will happen as a result of giving a high score, e.g. havi ng to undergo further unpleasant diagnostic procedures, or disappointing their family, or n ot being allowed to do a desired activity. One source of the diffi culty is the campaign to treat pain scores, particularly self-repor t pain scores, as the \200\230fi ft h vital sign. \200\231 In prac- tical terms, that mean s recording a single pain intensity score sim- ilar to a temperature, blood pressure, or he art rate score. Unlike the true vital signs, such pain scores represent a massive over- sim plifi cation. To make valid decisions about pain management requires a variety of additiona l information. Berde and McGrath ( 2009 ) stated that \200\230it remains a clinical art to combine patients \200\231 reports, behavioral observation, and physiologic measurement wit h the history, physical exam, laboratory information, and over- all clinical context in gui ding clinical judgments and therapeu- tic interventions \200\231 (p. 474). An example of a situation evoking the need for skill in this \200\230clinical art \200\231 is outlined in the case example. \231 Children might be motivated to provide high pain intensity scores because they antic ipate some benefi t, e.g. being allowed to stay home from school, or avoiding chores, or el iciting increased parental care and concern, or obtaining desired medications. When a child \200\231s self-report pain scores do not seem to make sense to the caregiver, additional eff orts to resolve discrepancies are needed, as discussed in the following sect ions. Th e place of self-report in a hierarchy of pain assessment techniques Pasero and McCaff er y ( 2011 , p. 123) present a fi ve-step strategy for assessment that starts with (1) elicit ing self-report if possible. If the patient is unable to give a self-report, then the follo wing steps are followed in order. (2) Identify pathological conditions and events or proced ures that might cause pain. (3) Observe for behaviors expressing pain, possibly using an ob servational tool. (4) Solicit information from caregivers and family members. (5) Attempt a trial of physical, psychological, and/or pharmacological means of pain relief, to see if t he observed behaviors refl ect reduced pain. Case example: an implausible self-report pain score Clinical question: a 6-year-old male patient has emerged from anesthesia following hernia r epair and is being prepared for transfer to the pediatric ward. Th e intraoperative anesthe tic is presumed to be past its half-life at this time. Th e patient \200\231s body is rigid in an antalgic position (legs drawn up), he is whimper- ing, and he has a high heart rate. His facial expression appears to express strong pain. He is shown a faces scale to obtain his self-reported pain intensity. He points to the no-pain (0/10) face. Should this be acce pted as indicating that he has no pain, leading to a decision to defer or minimize analgesi c treatment? Interpretation: the self-report score of 0/10 in this instance can- not be reg arded as \200\230the gold standard, \200\231 that is, a score which, in the presence of co ntradictory information, must be taken as cor- rect. Th e self-report confl icts with (1) k nowledge of the clinical Interpreting self-report scores when they con \202 ict with observation and context A chil d might give a low self-report pain score when the context and the child \200\231s behavior suggest that pain intensity is high, or the converse (see case example). Th e correlation between self- report and observational scales of pain intensity in children is usually stat istically signifi cant but modest. For example, in a study SECTION 5 measurement of pain 374 of 3/10 can be achieved. However, there appears to be no research with children and adolesc ents on their understanding and utiliza- tion of comfort-function goals. context, namely, the fact that the child has had an operation which in most individuals pro duces pain, and the fact that the intraoperative analgesic is likely to be wearing off ; an d with (2) observation of his behavior, including his facial expression, vocalization, and physical rigidity. Alternate explanations for the 0/10 score include the following: the chi ld (1) did not understand or fully attend to the faces scale, or (2) did not want to upset his parent by reporting pain, or (3) was afraid of having to stay in hospital longer, or of having something painful done such as an injection if he admitted to pain on the faces sca le. Location of pain Patients, including children, oft en fail to report parts of the body that hurt besides the primary presenting problem or the operative site, so specifi c inquiry is recommended. For example, children in the postoperative period are sometimes more bothered by an intravenous catheter than by pain at the site of the operation. Self- report of the location of pain can be elicited by verbal questioning, or by asking the child to point to the aff ected parts, or by provid- ing a checklist of body parts, or by utilizing a body di agram (also referred to as a pain chart, manikin, or pain drawing). Th e latter methods are reviewed by von Baeyer et al. ( 2011 ). Research pres- ently available supports the abilit y of most children age 8 years and over to complete a pain chart unassisted, while younger children may be able to do so with adult support. Also promising for locat- ing pain sympto ms in younger children are picture boards as used in assistive and augmentative communicati on with children with handicaps; these require only pointing to one among an array of pictu res (Mesko et al., 2011 ). Good clinical practice would be to continue the assessment process as follows. (1) Ask the parents to assist with assessment based on pain behaviors they have noted in their child in the past. (2) Note the child \200\231s response to his parents \200\231 eff orts to dis- t ract or comfort him. (3) Administer intravenous analgesia and note the response aft er an a ppropriate interval (analgesic trial). (4) Make notes in the medical record of this informa tion, not only a pain score but also the narrative of additional informa- tion, for transfe r with the patient to the ward. (5) Recommend that a ward nurse or parents discuss the pain scale with the child later on when he is in less distress, so that he can use the scale in subsequent pain management. Pain qualities Sensory characteristics of pain, such as burning, aching, or pricking, may b e of diagnostic importance, particularly in dif- ferentiating neuropathic from nociceptive sources of pain. Th e Adolescent Pediatric Pain Tool (Savedra et al., 1993 ) includes a lis t of adjective descriptors for this purpose, adapted from the McGill Pain Questionnaire. Th e list includes words such as: annoying, bad, horrible (among aff ective descriptors); cru shing, itching, burning (among sensory descriptors); comes and goes, constant (among tempor al descriptors). Patients are asked to cir- cle the words that apply to their pain. It is d esigned for children age 8 and over. Temporal characteristics of pain It is common to ask for ratings of pain \200\230right now \200\231 or at the time of a painful procedure, in addition to ratings of pain intensity \200\230at its worst \200\231 and \200\230at its least \200\231 over a specifi ed time per iod. Particularly with recurrent and chronic pain, questions are needed to assess the frequ ency and duration of pain episodes: \200\230How oft en did you have this kind of pain in t he last week/month? \200\231; \200\230How long did this pain usually last each time you ha d it? \200\231. More reliable answers to these questions can be obtained via self-report pa in diaries, discussed later in this chapter. Pain interference Measures of pain interference assess the extent to which pain impairs chi ld and family quality of life, attendance and perform- ance at school, leisure and social f unctioning, maintenance of positive mood and mental attention or concentration, and other v ariables refl ecting general functioning. Th ese are relevant both to acute pain (e.g. inte rference with postoperative ambulation) and chronic pain. An example of such a measure is t he brief eight- item PROMIS Pediatric Pain Interference Scale (Varni et al., 2010 ), which contains items such as \200\230I had trouble moving around when I had pain \200\231 and \200\230it was hard for me to pay attention when I had pain \200\231. (For further informat ion see Th am et al., Chapter 41 , this volume.) Desirable features of self-report measures of pain Tools for collection of self-report shou ld have as many as possible of the features listed in Box 36.1 (Hester et al., 1998 ; Paser o and McCaff ery 2011 ; von Baeyer 2006 ). Th e self-report scales recom- mended in this ch apter have most or all of these characteristics. How are self-report measures validated? Validation of self-report measures is inherently pr oblematic because self-report refl ects internal experience that is not accessi- ble by oth er means. Articles about pain assessment oft en describe a scale simply as \200\230reliabl e and valid \200\231. Th is refl ects a misunderstand- ing of the nature of validation, whi ch is not a one-time occurrence but a gradual process of accruing and weighing evidence for the ability of the scale to make accurate predictions or discrimina- tions in a variety of clinical contexts and with diff erent clinical populations. In systematic reviews, a scale is generally considered adequately validated for research and clinical use in a particular context if multiple studies of good methodological quality from diff erent research groups have demonstrated one or more types of validity for that context. Comfort-function goal: setting a target level of pain With children older than about 8 to 1 0 years, it may be helpful in making decisions on analgesic administration to inquire about the highest severity of pain that would still allow the patient to carry out valued activi ties (e.g. socializing, exercising, or attend- ing school). Th e question itself communicat es that pain relief might not be complete, and that the patient has a role in balancing the desired eff ects of medications with their side eff ects. For example, a child might have severe current pain of 8/10, requiring interven- tion, but might feel able to go to school when a target pain severity Several lines of evidence are commonly used to establish that a pain scale is reliable and valid for a particular clinical application CHAPTER 36 self-report: the primary source in assessment after infancy 375 ( Box 36.2 ). Validity of assessment tools is best demonstrated by multiple lines of eviden ce from multiple research groups in multi- ple and diverse clinical samples, as compiled in systematic reviews (e.g. Cohen et al., 2008 ). Box 36.1 Desirable features of self-report measures of pain \231 Evidence for validity and reliability in the current clinical context. \231 Developmentally and culturally appropriate, that is, within the Children with mild developmental delay or communication impairment Estimation of pain inten sity in children with moderate to severe neurological impairment relies primarily on observ ational measures (see Belew et al., Chapter 16 ; MacLaren Chorney and McMurtry, Chapter 37 , this volume). Few studies have examined self-report measurement in this population (Benin i et al., 2004 ). Children with mild impairment, or a mental age above 4 years, can sometim es use self-report measures designed for young children (Fanurik et al., 1998 ). However, n urses oft en overestimate the ability of cognitively-impaired children to use self-report s cales (Fanurik et al., 1998 ). Children with mild cognitive impairment should, in general, be given a chance to use self-report scales suitable for their mental age, and the resultin g scores can be supplemented or sup- ported by observational measures. child \200\231s cognitive, language, and social skills. \231 Easily and quickly understood, and well accepted by patients and clinicians. \231 Easily used with the patient to set pain management or func- tional goals (e.g. use the scale to indicate a target pain intensity as a guide for pain management or for plannin g physical exercise). \231 Places low burden on clinician to administer, score, and record. \231 Free or inexpensive and easy to obtain, reproduce, and distrib- ute (e.g. on the Internet). \231 Where physical materials are needed, these should be easily disinfected or disposable. \231 Available in multiple languages. Source: data from Pasero and McCaff ery, Pain assessment and pharmacologic management , Els evier Mosby, St Louis, Missouri, USA, Copyright 2011, and Hester et al, Putting pain mea surement into clinical practice, in Measurement of pain in infants and children (ed.) Finle y and McGrath, International Association for the Study of Pain Press, Seattle, USA, pp. 179 \200\223198, Copyright 1998. Measurement in chronic versus acute pain Self-report assumes special importance in chronic and recurrent pain, because the overt behavioral expressions of pain attenu- ate over time without necessarily being associated with decreases in the internal experience of pain. In other words, patients with chronic pain commonly report high levels of pain without showing overt expressions of pain, unless the latter are triggered by social or physical cues. Ass essment of chronic pain includes an emphasis on its consequences, including physical, emoti onal, and social func- tioning, thus requiring multidimensional pain questionnaires and int erview protocols. Box 36.2 Lines of evidence for validity of pain scales. Examples of studies employing each line of evidence to support self-report measures of pain intensity are cited by von Baeyer ( 2006 ) \231 Correlations (or similar measures of association) of self-report ratings with other validated self-report scales administered at the same time. Such validity correlations are typically high, and it is good practice to set an a priori minimum such as r \211 0.7 in validating a new scale. (Simply indicating statisti- cal signifi cance is not adequate, bec ause in large samples very small associations are statistically signifi cant but are not me an- ingful indications of validity.) Multidimensional pain scales, that is, scales that measure diff er- ent dimensions, domains , or aspects of pain at the same time, are used mostly with recurrent and chronic pain cond itions. Such scales are available in both self-report and parent-report forms, including th e Varni/Th ompson Pediatric Pain Questionnaire (Varni et al., 1987 ) and the Bath Adolescen t Pain Questionnaire (Eccleston et al., 2005 ). Th e Adolescent Pediatric Pain Tool (Savedr a et al., 1993 ) similarly provides a body outline, a rating scale for pain intensity, and a checklist of descriptive words. Self-report measures of pain have also been published for some specifi c recurrent and chronic disorders such as abdominal pain (Malaty et al., 2005 ) and head- ache (Budd et al., 1994 ). \231 Correlations (or similar measures of association) of self-report ratings with valida ted observational pain scales administered at the same time. Th ese correlations are typica lly moderate, and it is good practice to set an a priori minimum such as r \211 0.4 in va lidating a new scale. Tools to elicit self-reports of pain intensity are generally similar for acute and chronic pain. Pain diaries are used to track fl uctua- tions in pain intensity, interference and co ping over time (Palermo, 2009 ; Stinson, 2009 ). \231 Accurate ranking of hypothetical no pain, moderate-pain, and high-pain events depicted in pictures or stories. \231 Increased pain ratings in response to painful clinical or experi- mental procedures. Gender and cultural issues While sex diff erences are widely reported in the prevalence and intensity of pain, no studies to date suggest that pain must be assessed using diff erent methods in boys versus girls. Th e most salient sex diff erence in the pain assessment proc ess reported to date may be the ability of girls to discriminate between pain intensity and pain unpleasantness at a somewhat younger age (around 8 years) than boys (around 10 years) (Goodenough et al., 1999 ). \231 Decreased pain ratings in response to analgesic interventions or less painful ways of performing a procedure. \231 Decreased pain ratings over successive minutes, hours, or days of postprocedure, postoperative, or postinjury recovery. Source: data from von Baeyer, C. L, Children \200\231s self-reports of pain intensity: Scal e selection, limitations and interpretation, Pain Research and Management , Volume 11, Issu e 3, pp. 157 \200\22362, Copyright 2006, Pulsus Group Inc. SECTION 5 measurement of pain 376 By contrast, much research has focused on adaptation of self-re- port tools to diff erent c ultural, ethnic, or racial groups. Commentary on pain assessment in sub-Saharan Africa is p rovided by Walters ( 2009 ). One of the best-known faces scales, the OUCHER, is published i n separate versions displaying Caucasian, African American, Hispanic, Asian, and First Nati ons (North American Aboriginal) children. Th e Faces Pain Scale \200\223Revised and the Won g- Baker FACES Pain Rating Scale have both been used around the world; psychometric studies on the FPS-R have been carried out in Australia, Brazil, Canada, Spain, Th ailand, and USA . Inuit children and adolescents in the Canadian Arctic prefer the standard Wong- Baker FAC ES Pain Rating Scale to a version with pictures adapted for the Inuit culture, although old er adults prefer the latter (Ellis et al., 2011 ). Th e three most-researched faces scales appear to have acceptable utility in many cultures and countries. Box 36.3 Recommendations for clinical practice, education, and research \231 Use self-report measures as the primary source in a hier- archy of pain assessment m ethods (Pasero and McCaff ery, 2011 ) (followed by consideration of probable sources of pai n, observation of behavior, obtaining parents \200\231 report of pain behaviors, and conduc ting a trial of pain-relieving treatment.). \231 To the extent that the clinical situation requires and permits, obtain self-report o n all of the relevant domains of assessment (see Table 36.1 ). \231 Obtain and record the child \200\231s self-report of pain intensity, loca- tion, and temporal and sensory features on initial assessment and at intervals following treatment. Self-report using new technologies Rapid development is occurring in the use of smart phone s, com- puters, and web-based applications to elicit, record, and analyze self- reports of pain (Stinson, 2009 ; Stinson et al., 2008 ). Documented advantages of such technologies in clude the following. \231 For measurement of pain intensity, use a validated scale, e.g. the NRS from age 8 up , one of three faces scales from age 4 up, or the Pieces of Hurt for age 3 to 6. \231 Use consistent verbal anchor phrases for maximal pain, such as \200\230most pain \200\231 or \200\230worst pain you could have, \200\231 without embel- lishment or variati on between patients. \231 In numerous studies, adolescents and children as young as 4 years prefer computer ov er paper-and-pencil measures. For example, in a study of hospitalized children, 87% of thos e who expressed a preference preferred a handheld computer over paper for admin- istration of the Faces Pain Scale \200\223Revised (Wood et al., 2011 ). \231 For children with mild developmental delay, use self-report measures suitable for their mental age. \231 Compare pain intensity scores across time within individuals, not across children, b ecause the scores have diff erent mean- ings for diff erent people. \231 Th ese technologies reduce the burden on caregivers in adminis- tration and scoring of measures. \231 Institutions should select a small set of scales for regular use by staff that cover s the range of ages and clinical conditions typically encountered. Such a set might include NRS for older children, a faces scale for younger children, and one or two appropriate obs ervational scales. For chronic pain, one or two multidimensional questionnaires or intervie ws should be selected. \231 Th ey reduce or eliminate backfi lling, that is, the common ten- dency for people to skip diary entries and then fi ll them in later. \231 Th ey lend themselves to integration in electronic medical records (EMR) and automat ed databases: scores can be uploaded auto- matically using Web or cell phone communication. A caveat in this context is that EMR systems oft en provide only a single data fi eld for a pain score at a particular time point in time, making it diffi cult to deal with (a) disc repant estimates from diff erent sources (self-report, parent observation, staff observatio n, clini- cal context), and (b) multiple ratings over time that come from a pain diary. \231 Remember that pain assessment is more than measurement of intensity: location, tempo ral, sensory and emotional features, and functional consequences of pain also require asses sment. \231 Take self-reports of pain into account when planning pain treatment and evaluating its eff ects. Future research on self-report It is generally assumed that assessing pain using pain scale s improves pain management outcomes, but evidence supporting this assump- tion is scant (Fr anck and Bruce 2009 ). Further research is needed on this topic, as discussed by Lee and St evens ( Chapter 35 , this volume). to develop an \200\230ideal discourse \200\231 in which the children \200\231s thoughts ca n be expressed without fear of giving a \200\230wrong answer \200\231 or being judged or c riticized. Th e social and cognitive barriers to eff ective communication with preschool-ag ed children about pain, and tar- gets for research on these issues, are discussed by Champi on et al. ( 1998 ). While the NRS is now well established for children 8 years of age and older, the validity a nd reliability of this tool in the hands of younger children who can count, at least by age 6 and 7, require further investigation (Castarlenas et al., 2013 ). Key recommendations Recommendations for clinical practice, education, and research on self- report assessment of pain in children are off ered in Box 36.3 . Preschool-aged children, 3 to 5 years of age, are oft en not asked for self-reports because their responses, even on simple pain intensity scales, are frequently eccentric and hard t o understand (Champion et al., 1998 ; von Baeyer 2006 ). Moreover, asking ques- tions is th ought to be a poor way to get information from young children, especially for strangers (Wi lkinson 2003 ). Instead, it takes extra time and special skill to interact with young child ren in order Conclusion Self-report is the primary source of information for assessment and measurement of pain, to be obtained whenever possible. But CHAPTER 36 self-report: the primary source in assessment after infancy 377 getting valid self-reports from children presents special challenges, particularly those yo unger than 6 to 8 years. instrument to assess the impact of chronic pain on adolescents . Pain , 118 , 263 \200\223 270. Ellis , J. A. , Ootoova , A. , Blouin , R. , Rowley , B. , Taylor , M. , Decourtney , C. , et al . ( 2011 ). Establishing the psychometric properties and preferences for the Northern Pain Scale . Int J Circumpolar Health , 229 , 274 \200\223285. Th is chapter has emphasized interpretation of the meaning of self-report scores in the con text of many biological, social, cogni- tive, and developmental infl uences. Tools suited f or diff erent ages are cited. An agenda for future research is suggested. Falanga , I. J. , Lafrenaye , S. , Mayer , S. K. , and T trault , J. ( 2006 ). Managemen t of acute pain in children: Safety and effi cacy of a nurse-controlled algorithm for pain relief . Acute Pain , 8 , 45 \200\22354. Self-reports of pain can be compared within individuals across time, but not between indivi duals. Th eir meaning is oft en idiosyn- cratic and may not agree with estimates of pain in tensity based on other sources, that is, observation of behavior and knowledge of the clini cal context. 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