Content validity for FACT-GOG-Ntx items
Items NTX1 - I have numbness or tingling in my hands: Numbness of the hands was commonly described as a lack of feeling or sensation that affected activities of daily living such as buttoning buttons, feeling and holding objects, and writing (Supporting quotations are shown in Table 5). Tingling of the hands was commonly described as a feeling of pins and needles, stabbing, or prickling. Patients reported that the numbness or tingling of the hands was often a constant sensation. During the cognitive interview, 26 of 28 patients (93%) said that item Ntx1 was relevant to their experience.
Item NTX2 - I have numbness or tingling in my feet: Patients described numbness in their feet as a lack of feeling or sensation. Tingling was commonly described as a feeling of electricity, vibration, or being asleep. Patients reported that their numbness or tingling was often a constant sensation that impaired mobility and affected daily activities. Twenty-five of 26 (96%) responding patients said the item was relevant to their experience.
Including numbness or tingling within the same item: We asked patients, “In your experience, do hand/foot numbness and tingling go together?” For hands, 18 of 27 patients (67%) stated that numbness and tingling went together. For feet, 20 of 26 patients (77%) stated that numbness and tingling went together. Patient 025 explained, “I’ll be trying to go to sleep at night…if I move my feet or I touch anything, it comes back-that tingling and that numbness.” During the cognitive interview, 2 of 28 patients (7%) thought that the concepts of numbness and tingling should be separated into two questions. For both NTX1 and NTX2, 100% of patients (28 of 28) indicated they were confident or very confident in their ability to provide a response to the items as they were written; none of the patients found the questions to be confusing. When asked which questions were difficult to answer, patient 031 identified the additional questions 3-4, which separated numbness and tingling in the feet, as most difficult to answer: “Some of the neuropathy questions (were difficult) where you had separate sensations but they should go together, like tingling and numbness.”
Item NTX3 - I feel discomfort in my hands: Over one third of patients (12 of 31, 39%) listed hand discomfort or pain as a symptom of their neuropathy during concept elicitation. Hand discomfort tended to interfere with everyday activities or "basically anything that involved my hands" (patient 033). Twenty-five of 28 (89%) cognitive interview participants said item NTX3 was relevant to their experiences.
Item NTX4 - I feel discomfort in my feet: Eighteen of 31 participants (58%) listed symptoms consistent with discomfort in the feet, including aches, pain, burning sensations, and abnormal sensations. Discomfort in the feet affected activities such as standing and driving. Patients also described feeling as if a small object was in their shoe or under their foot, which affected balance and walking. Twenty-five of 28 (89%) cognitive interview participants said the item was relevant to their experiences.
Discomfort vs pain: Patients overwhelmingly stated that “discomfort” was more consistent with neuropathy experienced in their hands than “pain” (23 of 28 patients, 82%). Likewise, 21 of 28 patients (75%) said that “discomfort” was more consistent with peripheral neuropathy experienced in their feet than “pain”. Patients described discomfort as general, more constant, less severe and less likely to interrupt daily activities than pain. Pain was described as throbbing, hurting, more severe, and more likely to stop daily activities. According to patients: “Pain came sometimes but discomfort was always there.” (PT 011) “I have more discomfort than pain.” (PT 019) “Because my experience is numbness and tingling which is not painful, doesn't hurt, (it is) just annoying.” (PT 023) “It is irritating as opposed to hurting.” (PT 025).
Mean responses on the discomfort and pain items are shown in Figure 1. Thirteen of 28 patients (46%) had identical responses to the items referencing discomfort in the hands and pain in the hands. Of the 15 patients (54% of the sample of 28) whose responses were different, all 15 reported more hand discomfort than hand pain. Moreover, of these 15 patients, 11 (73%) reported “not at all” in response to “I have pain in my hands” while reporting levels of hand discomfort ranging from “a little bit” to “very much”. Fewer patients (11 of 28, 39%) had identical scores for foot discomfort and foot pain. Sixteen of the 17 (94%) patients with differing scores reported more foot discomfort than pain. We investigated the significance of differences in mean responses using two-tailed t-tests assuming equal variance. The findings revealed significant group differences for NTX3 and Add-5 (P = 0.007) and NTX4 and Add-6 (P = 0.016).
Figure 1 Mean scores of hand and foot discomfort and pain items.
Item NTX5 - I have joint pain or muscle cramps: Seven of 31 participants (23%) listed symptoms consistent with joint pain or muscle cramps. These symptoms were impactful to patient quality of life. For example, according to patient 023, “It was my calves that were cramping and it was, oh, I don’t think I’d call it severe, but it was at least moderate to severe cramping. And it was pretty painful.” Over half of cognitive interview participants (15 of 28, 54%) reported the item as relevant to their experience.
Item HI12 - I feel weak all over: Five of 31 concept elicitation participants (16.1%) mentioned feeling weak. Feeling weak was used to describe neuropathy symptoms in the feet, hands, legs, and feet. Others noted weakness when describing the impact of neuropathy symptoms, such as difficulty walking. For example, “Sometimes I have weakness in general, like I’ll be walking and I feel like I’m going to trip” (patient 010). Twenty-two (78.6%) of cognitive interview participants said the item as relevant to their experience.
Item NTX6 - I have trouble hearing: Trouble hearing was not spontaneously mentioned as a neuropathy symptom in the concept elicitation data. Some support for this item came from the cognitive interviews; three of 28 (11%) participants reported the item “I have trouble hearing” as relevant. Of the 25 who said the item was less relevant, 22 did not have trouble hearing, and three reported having hearing problems prior to beginning treatment.
Item NTX7 - I get a ringing or buzzing in my ears: Ringing or buzzing in the ears was mentioned spontaneously by one patient in the concept elicitation interview. A quarter of cognitive interview participants (7 of 28, 25%) reported the item as relevant to their experiences. Of the 21 (75%) who said it was not relevant, 20 did not experience ear ringing or buzzing, and one was unsure if his ear ringing was a neuropathy symptom.
Item NTX8 - I have trouble buttoning buttons: Seven of 31 participants (23%) described limited fine motor function during concept elicitation that affected their ability to button buttons. The process of buttoning buttons was described as time consuming and frustrating, causing some to require assistance or avoid wearing clothing with buttons. “It (buttoning buttons) took more time and it was frustrating having fine motor function limited” (patient 020). A majority of cognitive interview participants (25 of 28, 89%) reported the item as relevant to their experience.
Item NTX9 - I have trouble feeling the shape of small objects when they are in my hand: Ten of 31 concept elicitation participants (32%) listed symptoms consistent with trouble feeling the shape of small objects in their hand, including difficulties feeling small objects that resulted in problems grasping or holding on to small objects. Furthermore, 24 of 28 cognitive interview participants (86%) reported the item as relevant to their experience.
Item An6 - I have trouble walking: Six of 31 concept elicitation participants (19%) mentioned trouble walking because of their neuropathy. “Because of the tingling and numbness in my feet it’s hard for me to find my balance, to figure out where my feet are in the ground. So I tend to be a little, you know, wobbly…kind of unsure footing” (patient 011). Patients’ comments about trouble walking ranged from fear of falling, practicing caution while walking, and having to limit or avoid activities, such as exercise. Twenty-four of 28 (86%) cognitive interview participants stated that the item was relevant to their experience.
Item NTX10 - I have pain in my hands or feet when I am exposed to cold temperatures: Twenty-three of 31 concept elicitation participants (74%) reported hand or feet pain when exposed to cold temperatures. Some likened the pain to being shocked, “If I touch cold things, I get little zings going through my fingers. It intensifies if it’s colder. Like if I pull something out of the freezer, sometimes I have to drop it because it’s too cold” (patient 010). Patients reported limiting exposure to cold items and temperatures because of the pain and discomfort. All 28 (100%) cognitive interview participants reported the item as relevant to their experiences.
Item NTX11 - I have difficulty breathing when I am exposed to cold temperatures: Three of 31 concept elicitation participants (10%) listed difficulty breathing when exposed to cold temperatures as a symptom of neuropathy. They described feeling their throat close, throat spasms, or choking when exposed to cold temperatures. They also described feeling like needles were sticking in their throat. While relatively few patients listed difficulty breathing when exposed to cold temperatures in the concept elicitation interview, those who reported the symptom rated its importance to quality of life high (mean score=8). Moreover, 16 of 28 (57%) cognitive interview participants reported the symptom as relevant to their experience.
Coverage of all patient-reported concepts on the instrument: To ensure that the instrument adequately covers symptoms of importance to patients, we considered whether symptoms reported by at least 20% of the sample (Table 3) during concept elicitation were represented in the FACT/GOG-Ntx. Nine symptoms fit this criteria: hand tingling, feet tingling, hand numbness, feet numbness, cold sensitivity in the hands or feet, discomfort in the feet, discomfort in the hands, impaired fine motor skills, and joint pain or muscle cramps. Each of these symptoms is included in the FACT/GOG-Ntx.